Everything has mostly been covered. Essentially everything is programmed ahead of time. Drivers (they are now called Technicians) can only select a program to run while the robot is in base.The base is the white area (ignore the middle line--it is irrelevant as highlighted in
this image. Two fields run opposite to each other. Other than one cooperative mission, the two fields have no other interactions. There is a border (usually made out of tape) around the field (plus a few feet). Only the referee and two drivers per team are allowed in this area at any given time.
You may want to watch the challenge release video.
The mission model cheat sheet that I made may also be of use.