Each of the folders you see above is a complete tutorial covering some subject related to Torque 3D.
The README.markdown files in each tutorial guide you through the code for that tutorial, which is included in each folder.
They are all complete 'games' under the t3d-bones structure, so they can all be run instead of the default game/main.cs file.
The tutorials don't necessarily have to be completed in a linear sequence, though if one tutorial follows directly on from another I'll mention it in the header. In particular, I can recommend skipping the_main_file and going straight to basic_level.
Enjoy!