If you are new to TIS, read the Getting started section, which gives an overview on TIS and gets you started on using the TIS Board.
If you want to learn how to develop TIS Solutions, you can do some of the exercises provided in the TIS Training section. If you want to setup and maintain a TIS system, you may be interested in the Deployment page.
The TIS Editor and the TIS Board contain detailled descriptions of their components, the TIS Admin (User Management) contains information for user administrators, and the Deployment section information on the TIS system for technical administrators.