I've attached one of out basic GarageBand courses to this thread [click the More Info button up top]..
For an overview of the Piano Roll editor, check out video #21:
For an explanation of Time Quantize, check out video #22:
The Automation button in the Piano Roll editor displays and lets you edit MIDI automation, like modwheel, pitchbend, and piano damper pedal data that may be part of a recorded performance. For a more general explanation of Automation, check out video #33:
When the Catch Playhead button is on, the display of what's current playing [the current position of the playhead] is always visible on screen.
If you want full access to the entire course [and all the other courses], you could sign up for a Library Pass here:
PS - If you have questions about multiple topics, please start different threads for the different topics