Basics
So, this is a staff. It is the landscape on which musicians can write down musical ideas - notes, duration, speed, instrumentation, volume, etc. It can all be represented here.
Different instruments all have different musical ranges, meaning some instruments can hit notes that others cannot. To accommodate these varying pitches which span through several octaves, we use CLEFS.
(what exactly is an octave? Take a quick look at the next page)
Above, we have the treble clef, and below we have the bass clef. We can see the relationship between the two clefs by seeing where middle C is -
As we continue to place notes beyond the staff lines - either above or below - we use ledger lines to indicate where we are. Clefs enable us to reduce the amount of ledger lines needed to represent a piece of music.