At its most basic, it's just a desk. Some workstations come as more complex packages. They may include a CPU cabinet, a file drawer or media storage. If a particular piece doesn't come standard, it's probably available separately. Put several workstations together, and you can construct a homogenous workgroup space.
Desks are often available in various sizes.
Some are also designed to fit into a corner. The main options you'll find to complement your workstation are hutches, peninsulas, file cabinets and storage drawers. We'll look at the Bush Mod 4000 collection to get an idea of a typical pricing structure. Hutches offer vertical space without sacrificing desk area. A peninsula attached to the main desk is the quickest way to expand working space.