Here is an example of a stave being used in a piece of music. This is an extract from the trumpet 1 part in "In The Stone" by "Earth Wind and Fire" (the extract starts 8 seconds into the video). As you can see there are lots of notes across the stave. The stave means you can read across the music from left to right and therefore follow it.

The first note is an F# as it is on the top line. We know this because there is a treble clef at the beginning (see the next section for details) and we know it is a sharp because it is on the first line, because there is a sharp on the same line at the very begging of the stave in the key signature (see key signature section).