Lines and spaces of the treble clef
Music is written on a series of five lines and four spaces known as the stave. These lines and spaces have no value or pitch of their own until a clef is placed on them. The lines and spaces are then assigned pitches according to the clef used.
In treble clef, the lines are assigned E, G, B, D and F (in ascending order) and the spaces are assigned F, A, C and E (in ascending order). You can see that when combined the pitches move up or down the stave by step.