Once you know know the Music Notes and common Music Terms & Symbols, you will be able to play the music you read. But what is the style of the piece? Is it Fast? Slow? Humorous? Solemn? Is the music getting faster? Getting slower? These aspects of music are covered in the Tempo Markings.

The Tempo sets the pace or rhythm of a piece and can be specified exactly by indicating the number of beats per minutes.

There are many music charts that set Tempo Markings to specific beats per minutes (Wikipedia for example) and, although this can give a general indication of the speed, one should never take these too literally. Composers have different styles and may change the pacing throughout a piece depending upon the mood.