A wheel manoeuvre is a basic turn performed by pivoting the unit around one of its front corners.
Performing a wheel is often the best way of making a modest alteration to the direction a unit is facing whilst still being able to advance. When performing a wheel, the leading edge of the formation moves forward, pivoting round one of the front corners. The unit swings round like the spoke of a turning wheel and completes the manoeuvre facing a different direction. You don't need to measure the distance wheeled by a charging unit, but during the Remaining Moves sub-phase, wheels are measured as follows:
When a unit performs a wheel, every model counts as having moved as far as the outside model. Once the wheel is complete, you may use any movement that the unit has remaining. A unit that is not charging can wheel several times during its move, and indeed can mix forward movement and wheeling, as long as it has enough movement to do so. Units are not allowed to wheel backwards.