Displays all of your files, modules, tasks, and functions. Clicking on a file will open an editor window with the file loaded.
The text editor does with keyword highlighting and links to other features. If desired, emacs or another editor can also be used as the default editor (with some loss of functionality).
The hierarchy window and class browser allow you to see how the modules of the design fit together.
The symbol view can also display the modules of the design and the tasks and functions. Clicking on any symbol in the design will open the editor to the correct location in the verilog source code.
If you are still having trouble locating something is a grep window that will search the entire project. Clicking on the grep results will take you directly to the source.