Projects allow users to keep a part of their preferences separately, in order to better accommodate separation of the work in multiple sub-tasks. For example, a common way of using projects would be to have one project per special-effects shot in a film. To this end, one would want, for example, to specify render directories that will differ from one shot to the other, without having to re-type them for every composition used within this shot. This is the kind of service that project management is intended for. By comparison, the User Preferences are more geared towards controlling the behavior of the user interface.
By default, project management is turned off in Toxik, but can be enabled by visiting the User Preferences (Edit->User Preferences). In the tab labeled General, enable the Project Selection Dialog setting and click OK or Apply at the bottom right. The project selection will be enabled for the next time you start the application.
When project management is turned off, Toxik uses a default project file that is called Default.txproject. You can view the location of this file by visiting the project preferences (Edit -> Project Preferences) and viewing the Information tab.