How To Read Ledger Lines
In music, the staff is a set of five horizontal lines and four horizontal spaces which are used as a template for identifying musical notes. These five lines and four spaces have the capacity to hold nine individual natural notes and their accidentals.

The notes of a staff whose letter names are designated by a treble clef go from the first E above middle C until the note F one octave above.


Likewise, the notes on a staff with a bass clef go from the note G two octaves below middle C until the note A just two letter names below middle C.


However, by just looking at the keyboard of a piano we can see that there are many more than just these eighteen notes allotted by both clefs.
Ledger lines are short lines placed above or below the staff which are used for notes that exceed the tonal boundaries of the staff.
For example, this key is two notes above the pitch which we just identified as being the top note of a staff with a treble clef.