Rhythm (timing, spaces, emphasis & overall speed): when you are playing a song there are points in the song that have no sound and points where there is sound. Drums are used to express a certain pattern that the song follows.
Emphasis on certain sounds in a song is done to give a sense of differentiation between the sounds.
The way in which you arrange these occurrences of sound, sound duration, and no sound, and the emphasis on chosen sounds, creates a phenomena called timing, and thus a rhythm for the music. The overall speed of the rhythm is also decided upon by the composer.
Note : These points of no sound between sounds within a song creates space between the sounds. That space of no sound could last for a fraction of a second or longer.
Rhythm that is familiar to the listener is desirable, as it gives predictability.
There are agreed upon types of timing • shown here.
There are agreed upon types of rhythm • shown here.
There are agreed upon types of speed • shown here.
A composer, as part of their own unique composing process, will choose the different instruments and voices to make the music and lyrics, and add to them a specific timing with its spaces, sound emphasis, & overall rhythm speed, so the desired emotional effect is infused into the listener.