Three "usage" options are available to choose from in a Custom install:
Workstation
This installs software packages suitable for a typical desktop workstation. This is the best choice if you intend to use the machine for normal, everyday tasks (web surfing, graphics, multimedia, office apps, etc.).
Server
This installs software suitable for a Linux-based server (email, web, ftp, etc.) As a server, don't expect the bells and whistles of a desktop workstation as servers run with minimal extra goodies.
Development
Choose this if you intend to use the PC primarily for software development. This will install a complete collection of software required to compile, debug, format source code, etc.