Trucking companies, or carriers, generally have a home office or terminal from which they run their businesses. At the terminal there are loading docks where trucks pull up to drop off and pick up their loads. The terminal also houses a maintenance area for repairs and safety checks on trucks, a warehouse where dockworkers work, and an office area where terminal managers, sales representatives, customer service representatives, and dispatchers work. Some terminals also offer amenities for drivers, including laundry facilities, showers, telephones, and wash bays.

A carrier may transport two types of freight shipments: truckload (TL) and less than load (LTL). Truckload shipments are made when a driver picks up a load from a shipper and delivers the entire load to a single company in another city. LTL shipments are made when a customer needs a shipment of cargo that cannot fill a large truck. A company that makes LTL shipments picks up cargo in small trucks and then delivers the loads to the terminal where the cargo is sorted and loaded onto larger trucks. The larger truck then delivers the freight to a terminal in a different city, where the cargo is sorted again and loaded onto smaller trucks for delivery in the city. TL shipment is less expensive than LTL shipment, because it is a more efficient use of space. Also, companies that deliver TL shipments can use nonunionized labor. LTL companies are the most highly unionized sector of the trucking industry.

The primary types of carriers in the trucking industry are private carriers and for-hire carriers. A private carrier is usually a division of a larger business operating its own fleet of trucks, which are used to ship its own products. A for-hire carrier transports someone else's freight either intrastate or interstate. Intrastate shipping is subject to state regulations, whereas interstate shipping is subject to federal regulations. The competition among for-hire carriers is intense, because in a sense they compete with private carriers. In many cases it is cheaper for a large business to ship by for-hire carriers than to maintain a large, expensive fleet.

For-hire carriers are the largest employers and offer the best wages in the trucking industry. They are divided into two groups: common carriers and contract carriers. Common carriers serve the general public, while contract carriers specialize in services for an individual shipper with whom they have a contract.

Common carriers provide pickup and delivery services, as well as long-distance shipping. Pickup and delivery operations transport general freight to specific distribution terminals, and this is a heavily unionized sector of the trucking industry. Carriers that provide long-distance shipping often transport special commodities and offer point-to-point service or deliver to distribution terminals in cities.

Contract carriers include owner-operator drivers, who are independent businesspeople that either have contracts with a variety of companies or lease their services to a certain company. About one out of eight truck drivers is self-employed, and a significant number of these drivers are owner-operators.

According to the American Trucking Associations (ATA), there are about 3.5 million truck drivers working in the United States. The Department of Labor reports that as of May 2019, the general freight trucking industry employed a total of about 1.5 million workers across all occupations.

Several different classes of workers serve as administrative support personnel. Dispatchers coordinate the movement of freight and trucks and stay in contact with drivers as well as with freight customers, often by radio or telephone. Traffic, shipping, and receiving clerks keep records of shipments arriving and leaving and verify the content with shipping logs. Billing clerks maintain company records of negotiated shipping rates and prepare customer invoices. Diesel mechanics perform all types of maintenance and repairs, including engine rebuilds on trucks. Mechanics are sometimes promoted to parts managers in charge of keeping the supply of replacement parts. Helpers, laborers, and material movers help load and unload freight from trucks. Executive and managerial staff provide general direction to the trucking company. Logistics engineers work with customers to help plan the best way to ship their goods.