Just for info, the musical alphabet consists of only the first seven letters, but it starts on C rather than A. So it goes:

C D E F G A B - then back to C, in a repeating loop

If you're going up the scale/staff it goes in the above order.

If you're going down the scale/staff it goes backwards, i.e. B A G F E D C


On that chart in the link I gave above, the # (sharp) sign next to to the F (F#) means it's halfway between the notes F and G: a little higher than F but a little lower than G.