Bass clef

This is the symbol for notes below middle C - in piano music, a bass clef is often used for the left hand.

The spaces are:

A.C.E.G.   All Cows Eat Grass

And there are a few ways to remember the lines:

G.B.D.F.A. Gorillas Buy Donuts From Asda
           Great Big Dogs Fight Animals
           Green Buses Drive Fast Always
           etc

Treble clef is above middle C. Also see other clefs.

The notes above and below are on leger lines.