Is average speed similar to velocity?
Speed and velocity are similar, but not exactly the same.
Speed describes how much distance the object is moving over in a given amount of time. Speed is what we call a "scalar" value, meaning that it could be imagined as some point along a sliding, linear scale of values, from 0 to infinity. Speed is a component of velocity.
Velocity is not a scalar value; it is a vector. Vectors describe both a speed and a direction. You could have multiple vectors, all of which have the same speed, but all of them pointing in different directions. When working with physics problems it's important to remember that the vector nature of a velocity measurement strongly influences the way that it interacts with other things; for example, two velocities can cancel each other out if they're going in opposite directions. Furthermore, the reference frame of one velocity might cause other velocities to appear "negative". Speed, on the other hand, will have the same value regardless of direction and this will make it difficult to evaluate relative speeds between two or more objects.