Tempo is the speed of a composition or some of its parts. It gives us an understanding of how fast we need to play a particular piece of music. We find these instructions above the musical staff. But the problem is that the tempo can be marked differently.
A metronome mark in beats per minute, bpm, indicates the precise tempo. The indication includes the value of a musical note and the number of oscillations of the pendulum. The given musical note lasts for the given part of one minute.
Tempo marks are Italian terms. Their literal translations tell that a piece of music is slow or moderate, quick or very fast. These marks are not concrete. However, we have an approximate range of bpm for each term.