[Delian]

Tank Drive Uses two joysticks, the y-axis of each joystick, i.e., up-down, directly maps to the two motor values.

Arcade Drive uses a single joystick. The value of one of the motors is the y-axis plus the x-axis, while the value of the other motor is the y-axis minus the x-axis. This makes it so that pushing forward on the joystick moves both forward, pushing to the left spins counter-clockwise, etc.

Any other questions?