Tanks are tracked vehicles with each track independently controllable. Speed and direction are controlled by how each independent track is used. For each track control, further forward or further back causes that track to move more quickly in the selected direction.
As tanks move across terrain, they are affected by qualities of the terrain. Loose terrain like sand or soft terrain like a swamp would slow a tank compared to firmer ground.
If a tank fires while moving, the recoil of its cannon will have an impact on momentum, slowing progress in the direction of the cannon and speeding up progress away from the direction the cannon is aimed. If the cannon is aimed across or partially across the axis of its momentum, firing will impart sideways energy.
In addition to controlling movement of the tank, there are controls for aiming the cannon. The cannon is mounted in the top turret and can rotate relative to the body of the tank. This requires an additional control. Also, there must be a control for firing the tank’s cannon, and additional controls for any other weapons or equipment the tank operator might employ.