Cheat Engine

[CiaoCiaoxD]

Hello everyone, I'm an Italian guy and not knowing English I'm using google translator xD

anyway ..
I have problems in making a scan AoB (Array of Bytes)
I'm trying to create hack for facebook, and I think we can, as many create them: D

when I do a scan, they tell me that first I have to find some static byte to put * (willcards) or ? (I think they are the same)
I now have a couple of questions for you
What is different between * and ** I've seen in the cheat table that contained both * and **
and what changes between ? , and ?? (willcards)

also how can I do to find the bytes static?
please let let me explanations in brief

please let you respond? thank you very much