At the beginning of each piece of music, after the bass clef, is the time signature e.g.:
The time signature indicates the number of beats per bar (the top number) and the type of note receiving one beat (the bottom number).
* is the most common time signature used and is sometimes represented by this Q symbol called Common Time.
Tempo indicates the speed of a piece of music and is measured in beats per minute. E.g., 3 = 60 would indicate that each quarter note has a duration of 1 second.