Practically, there is only one crucial difference between speed and velocity. If shortly, it might be said, that velocity is the speed with direction. Now, let me explain.
When talking about speed, we care only about how fast the object is moving. This turns speed to a scalar quantity, for here we measure only how fast the object covers the distance in space. Things are pretty simple here. The faster the object moves, the larger is the covered distance in the specific amount of time. Should the object move slowly, it would cover a small amount of space in the same amount of time. No movement means no speed.
On the other hand, when talking about velocity, we need to consider direction as a part of a process, for velocity is a vector quantity. So, for example, if somebody takes one step forward and then one step back (and returns to the original starting position) - no matter how fast it is done, it would have zero velocity. To gain any amount of velocity an object has to move in space and change the position by maximizing the amount of displacement. So, velocity is direction aware, and when describing the object’s velocity it is not enough to mention f.e. 35 mi/hr, you need to add direction. So, the right variant would be 35 mi/hr, west.