BCC means blind carbon copy (in the old days it meant when you sent a memo to more than one person you did not list everyone receiving it). In the context of e-mail, it means that others canot see the e-mail address of all those receiving an e-mail (and hence get access to the addresses of others receiving the e-mail).
You're not thick, the computing and gaming world is full of TLA's (three letter achronyms) and you can't know them all! You won't know, unless you ask.