All modules have some built in documentation, you can use F1 on a selected module to see it. When doing for this the first time (or after a program upgrade) the program may have to regenerate the help files, causing some display clutter. The information will be shown in your default web browser.

When no module was selected the module info file will still be opened with F1 without going to a specific module.

Right click on a module and select Help from the popup menu, this will show the same description as the generated help file without opening a browser.

Also when you hover the mouse cursor over the module selector with the mouse, popups will be shown with some even more compact information along with an image of the module.

The generated help information is also used as a cache for module images to make them look a bit nicer when you hover the mouse over the buttons in the module selector.