Quite literally, the drone “banks” in order to travel in ANY direction.
Forgive the over-simplification as there is a significant amount of physics involved, but imagine that in order to move forward, the rear props increase in power/speed, or the front two decrease in power/speed, so that the aircraft tilts forward.
That then forces the thrust of the propellers more rearward, creating forward motion.
The same occurs for side to side motion... the two props on the right increasing in power will tilt the craft up on the right, which forces the aircraft to move left, etc.
If the aircraft is already moving forward and receives input to “turn” left, then it will “bank” simply due to physics... forward momentum + left turn creates “banking” effect since the aircraft must tilt to change the direction of thrust.
Again, simplistic, but does that help make sense?
This is exactly why these aircraft fascinate me... the amount of technology built in to them that allows us to fly them so easily is mind bogglingly awesome.