Usually, we consider motion with respect to the ground or the Earth. Within the Universe there is no real fixed point. The basis for Einstein's Theory of Relativity is that all motion is relative to what you define as a fixed point. In order to determine how fast an object is going, you measure the time it takes to cover a given distance. The terms speed and velocity are similar, but they mean something slightly different.
Speed is how fast something is going.
Velocity indicates the speed of an object in a direction of motion. For example, if you say a car is going 30 mph, you are talking about its speed. But if you say it is going 30 mph in a north direction, you are talking about its velocity. We distinguish between speed and velocity because if you add the speeds of objects, their directions are important. For example, the velocity of an airplane with respect to the ground would vary according to the direction of the wind.