Tempo
Tempo is the term simply meaning the speed of the music. For musicians this is written in the terms of beats per minute (BPM). There are terms for the speeds of music such as Andante meaning slow at a walking pace (approximatly 90bpm) and Allegro moderato meaning moderately fast (approximatly 120bpm). Below I have a couple of clips to demonstrate these BPMs from a metronome. The louder click at the beginning is the beginning of a measure which is a unit holding a set number of beats (in our case 4).
Keeping the Beat
A personal tip for anyone struggling to keep the time is to tap your foot. Tapping your foot to the beat helps wind instruments and percussionists since they do not use their feet for playing. For pianists it is best to keep the flow of your movements with the beat to maintain tempo.