There are several different clef signs that are used in reading music, but there are two that most commonly used. The treble clef (or G clef) and the bass clef (or F clef).
Music is noted on what is called the staff, which is five horizontal lines that notes can be placed on (line notes) or between (space notes).
Each line and space on the treble clef staff has a letter name from A to G. The spaces from bottom to top are F-A-C-E. The lines from bottom to top are E-G-B-D-F.
Like the treble clef, each space and line on the bass clef has an assigned letter name from A to G. The spaces from bottom to top are A-C-E-G and the lines from bottom to top are G-B-D-F-A.
Notes can be written above or below the staves by adding additional lines called ledger lines. Continue to count up or down in alphabetical order to identify these notes.
Learning to read music is a process and requires practice to fluently read notes in the context of a song. Flashcards (available online or at local music stores) can be a helpful tool in developing music reading skills.