Piano music is read by placing notes on 2 staves of 5 lines each.
This comes from the Great Staff system with each line and space having a letter name.
The letter names used in music are A, B, C, D, E, F, G (at G, the names repeat beginning with A).

Notes on eleven lines and ten spaces (Great Staff) can't be read at a glance. At times you would have to stop and count to find the name of the note.
So five lines are used. This is called a staff.

You'll notice on the 2 staves (above), two signs.
The top is called the Treble (high) or G clef .
The bottom is called the Bass (low) or F Clef.
With a little closer look you can see the final curve of the G clef wraps around the second line from the bottom of the top staff. This curve is around the line G.
Now if you glance at the bottom clef, you'll see the two dots on either side of the second from the top line which is F.
The notes of the Treble clef are usually played on the piano by the right hand.
The Bass clef notes are usually played by the left hand.
Below are the notes on the two staves.

There are 3 sets of letters from A-G. As you move upward the notes become higher.
All A's for instance sound the same pitch or note, however, one A note is higher (an octave) than another.
For instance if a man and woman sing the same song, even though they are singing the same pitch (A), the man's voice is singing lower than the woman's.
The man's voice may be sounding tones from the light green section while the woman's voice is sounding tones from the dark green section.
Below are the two clefs with the letter name for each line and space.

Notice the letter C in the middle which adds the eleventh line, completing the staff system (like the Great Staff). This is how the name Middle C came about.