What is fast tempo?

The tempo of a song is the speed at which it is played. This speed is determined by the beats per minute. More beats in a minute means the tempo is faster.

Fast tempos are listed below (from Wikipedia):

Allegro is 120-139 bpm

Vivace is 140 bpm

Vivacissimo is really fast

Allegrissimo is faster

Presto is 168 to 200 bpm

Prestissimo is more than 200 bpm

Basically, anything over 120 bpm is a fast tempo.