Forgive my ignorance, and I'm
really really sorry if this has already been answered before (I
have used the Search Option!!), but... Just what
is an Attack Modifier?
F.I., I've got a lightsaber with, amongst other things, an attack modifier of +7. I went through crystal-testing hell to get a satisfying balance between damage and att.mod. just to realise that I really have no idea how useful an att.mod. really is.

So what does it do?
P.S. Forgive the irritatingly annoying amout of italics used in the first paragraph.