Im just learning sheet music and don't understand the multiple Ledger lines, not sure if i should be asking this here but i can't be the only one that's not sure about it.
Hopefully this answers your question:
There are commonly five ledger lines that collectively make a "musical staff". These ledger lines help you visually see where exactly a note is. For example, when you look at a musical staff (which is a collection of five ledger lines), you should look to what the "clef" is on the very start of the page (is it a bass clef, treble clef?) the clef tells you where middle C is on your instrument. Let's say you are in treble clef (G clef). The first note that is just below the lowest ledger line is a D. If a musical note is placed ON the lowest ledger line, it's an E, and continue up from there. A note just above the first ledger line is read as an F, just above that on the next ledger line is a G, above that in the space is an A, above that on the next ledger line is a B, and above that in the space is a C, on and on and on. People take short cuts to remembering what these ledger lines and spaces represent as far as the notes that would be placed on them. In the G clef, just remember " F A C E". F is just above the first ledger line. A is above the second one, then C, then E. Notes that are ON the ledger lines in the G clef are "E G B D F". If there was only one ledger line, notes would just be floating on the page and not tell you what they are. Only some percussion instruments have sheet music that has single ledger lines (I think) because they read beats instead of notes.
The answer to the question in your comment below is no, the notes never change, ever. Even in abstract post-tonal music that is extremely complex and doesn't even have a key for which pieces are center in, the notes are always the same. The only time you need to worry about reading a musical staff differently is if the staff has a different clef. For example, if you're reading the F clef (bass clef), there are set particular notes for that clef (and I could go on explaining what the notes are in the bass clef if that's needed) but if the clef is treble clef (G clef), or really any clef whatsoever, it doesn't matter whether you are in C major, D minor, F-sharp major, or A-double flat major, "THE CLEF SETS IN STONE" what the notes are in and between those ledger lines. Hopefully this helped.
P.S - totally my bad for originally saying the bass clef was c clef! That would be the alto clef. Silly slip!