What is angular speed and angular velocity?
That is analogous to linear speed and velocity, but for
rotation. Whereas a linear speed (or velocity) is expressed in
meters per second (or some other units of distance / time), the
angular speed or velocity is expressed in radians / second (or some
other units of angle / time).
Of course, when something rotates, there is also a linear speed,
but different parts of an object rotate at different linear speeds,
whereas the angular speed is the same for all parts of a rotating
object - at least, in the case of a solid object. For example: the
Earth rotates at an angular speed of 1 full rotation / day. The
linear speed at the equator is approximately 1667 km/hour; close to
the poles, the linear speed is much less.