Velocity is the measurement of speed included with a direction. Both speed and direction are measured relative to some fixed object (in most cases, our planet earth). The numerical value of speed can be represented as a negative, which would indicate the opposite direction as indicated.
Velocity can be calculated from by the following expression:
The arrow above the velocity variable v indicates that it is a vector variable, and has some direction.
Please see below to convert among various units for velocity:
The train was moving at 50 km/h west.
The Frisbee was thrown with a horizontal velocity of 10 m/s
After the accident, the car was traveling at a velocity of -2 km/h
Hyperphysics has a more detailed discussion of velocity.