Velocity is speed with a direction. Speed does not have a direction. It is a measurement. Speed is the magnitude of velocity.

In non-scientific usage they are the same. Speed is more common, velocity would be used more in scientific terms but could be a synonym for speed if you wanted to spice up your writing / speaking and sound more intelligent. Scientifically, Speed is what is called a "scalar" quantity, Velocity is a "vector" quantity. If these mean nothing to you, don't worry. ;-)

Speed = quickness of movement. The rate at which something moves Velocity = is used more formally in physics, for example, and is used when one is talking about the speed of inanimate things. You would talk about terminal velocity, but not terminal speed.

Same but speed is the layman's (normal!) term and velocity is the scientific (physics) term. I believe velocity is "how fast something travels in a given direction" but you may need a scientist to explain it properly...! :-)