Rhythmic notation shows when to play those notes & for how long. This is the most essential information. But it only shows how fast or slow to play the notes relative to each other. It doesn’t tell us how fast or slow to play the piece overall.

That is what tempo is for. Tempo is usually indicated in either of two ways.

1. General indication – such as “slowly” or “quickly”. Classical pieces frequently use Italian words like “adagio” or “allegro” – which mean respectively “slowly” or “quickly”. Often some “quality” description will be given with the tempo indication.
2. A much more accurate and objective manner of specifying tempo is in Beats Per Minute (BPM). Literally it means how many beats occur per minute of time that passes. This is easily quantified by using a metronome – an absolutely essential tool every musician should have for practicing.

So, if you are playing quarter notes in a piece that is indicated to be played at 60 beats per minute (hereafter BPM), you will play one note every second. If you are playing eighth notes at 60 BPM you will play two notes every second – one on the second and one evenly spaced in between every second.

Here is a list of common tempo terms with their typical Beats Per Minute equivalents.