While supply chain is a very broad career field, it has 7 primary functional areas: Purchasing, Manufacturing, Inventory Management, Demand Planning, Warehousing, Transportation, and Customer Service.  These areas may appear to be independent functions, but in an efficient supply chain, they must interact to a great degree and are very dependent upon one another.    

Purchasing:   The activity of acquiring goods or services to accomplish the goals of an organization.

The major objectives of purchasing are to (1) maintain the quality and value of a company's products, (2) minimize cash tied up in inventory, (3) maintain the flow of inputs to ensure  the flow of outputs, and (4) strengthen the organization's competitive position. Purchasing may also involve (a) development and review of the product specifications, (b) receipt and processing of requisitions, (c) advertising for bids, (d) bid evaluation, (e) award of supply contracts, (f) inspection of good received, and (g) their appropriate storage and release.*  Business Dictionary.com 

The purchasing function is core to any company, as it provides the materials and resources needed to create a product.   As the economy becomes more global, the opportunities become even more exciting.  The roles that exist within this function are numerous, and here are just a few:   coordinator or analyst, materials manager, corporate purchasing manager.   These roles can exist at a field location such as a plant or at a corporate location.   Depending on the company, individuals could be involved in purchasing anything from office supplies to parts for the construction of airplane engines.   

Manufacturing:  is the production of merchandise for use or sale using labour and machines, tools, chemical and biological processing, or formulation. The term may refer to a range of human activity, from handicraft to high tech, but is most commonly applied to industrial production, in which raw materials are transformed into finished goods on a large scale. Such finished goods may be used for manufacturing other, more complex products, such as aircraft, household appliances or automobiles, or sold to wholesalers, who in turn sell them to retailers, who then sell them to end users and consumers.   Wikipedia

The manufacturing function has received a lot of notice in the press as companies move various production operations overseers.  Despite this, there are still many job opportunities available.  These include:  production planner, production manager, corporate manager of production planning, plant manager, line operator, machine operator, QA analyst, or engineer.  Manufacturing will always play a key role in the US economy as many products will always  be produced here.   From food to cars, companies will continue to manufacture in the US because of the  skilled workforce and natural resources available.   

Inventory Management: Activities employed in maintaining the optimum number or amount of each inventory item.

The objective of inventory management is to provide uninterrupted production, sales, and/or customer-service levels at the minimum cost. Since for many companies inventory is the largest item in the current assets category, inventory problems can and do contribute to losses or even business failures.   Business Dictionary.com

The management of inventory is a key function of any manufacturing company, whether domestic or foreign.  Physical inventory is often one of the most signification assets of a company, and without it, a company would have no sales.   Its important to have the right product, at the right place at the right price, and inventory allows this to occur.   In todays global economy the inventory function has become more important and challenging as product can be produced and available anywhere in the world.   

Demand Planning:   is the process of forecasting customer demand to drive execution of such demand by corporate supply chain and business management. Demand forecasting involves techniques including both informal methods, such as educated guesses, and quantitative methods, such as the use of historical sales data and statistical techniques or current data from test markets. Demand forecasting may be used in production planning, inventory management, and at times in assessing future capacity requirements, or in making decisions on whether to enter a new market

Demand forecasting is predicting future demand for the product. In other words it refers to the prediction of probable demand for a product or a service on the basis of the past events and prevailing trends in the present.  Wikipedia

Demand planning today requires analytical skills and a love of computer modeling.  It helps if you have a crystal ball, but since few people do, the art and science of forecasting what people will buy, or what components you will need, or what trends will impact the sales of your product is left to those who can analyze and interpret data effectively.  

Warehousing:  Performance of administrative and physical functions associated with storage of goods and materials. These functions include receipt, identification, inspection, verification, putting away, retrieval for issue, etc.  Businessdictionary.com.

While many people view the function of warehousing as the simple process of storing products, it has evolved into a function that does more than that.   In today’s world of mass customization, the warehouse has evolved into a distribution center, and even a facility to customize the final product via repacking, labeling or other physical conversion.   The importance of these facilities has grown as it’s the final “stop” before moving to the customer.   Proper handling, storage  and management of the products within these facilities must occur so that customer orders can be fulfilled with the right product at the right time.   

Transportation:  is the movement of people, animals and goods from one location to another. Modes of transport include air, rail, road, water, cable, pipeline and space. The field can be divided into infrastructure, vehicles and operations. Transport is important because it enables trade between persons, which is essential for the development of civilizations.  Wikipedia

The transportation function is critical to the supply chain because it is where the rubber literally meets the road.   A company can have the right product at the right warehouse at the right time, but without transportation if won’t make it to the customer at the right time.   In todays global economy, this function is even more critical as its no longer as easy as putting a product on a truck and having it delivered.  Now it might be shipped via container ship, airplane, train, truck or even uber car before arriving at the customer.   Companies have to evaluate the many different dimensions of each option such as cost, speed, reliability and ability to service when deciding which to utilize.  

Customer Service: The process of ensuring customer satisfaction with a product or service. Often, customer service takes place while performing a transaction for the customer, such as making a sale or returning an item. Customer service can take the form of an in-person interaction, a phone call, self-service systems, or by other means.  Investopedia.com

While the customer service function appears to be at the end of the supply chain, it is definitely not the end of the process.   This function is critical in that its works to meet the needs of the customer and ensure the customer receives what they want, when they want it.   This function is sometimes the only point of contact a customer has with a customer so its imperative that they have the skills and knowledge to understand a customers needs..and to meet those needs when possible.   

Within each of these functions there are many different types of roles:

Types of roles in supply chain:

Demand Planning:  demand planner, demand planning manager, 

Purchasing:  coordinator or analyst, materials manager, corporate purchasing manager

Manufacturing: production planner, production manager, corporate manager of production planning, plant manager, line operator, machine operator, QA analyst, engineer,

Inventory:  inventory analyst, inventory manager, cycle counter, deployment planner/manager, deployment planner

Warehousing:   forklift driver, order picker, supervisor, operations manager, inventory analyst/manager, customer service, dock scheduler, corporate warehousing analyst/manager

Transportation:   driver, dispatcher, engineer, asset manager, brokers, corporate transportation analyst/manager

Customer service:   customer service coordinator, VMI (vendor managed inventory) analyst, manager, import/export analyst/manager

Other supporting roles:    IT, HR, Project management, engineering, Marketing  (for 3pl companies), Sales (for 3pl companies), finance, accounting.