new poster, with questions!

I've been a member for a little while, but not very active on the forums. I was curious if you guys could help with your abbreviations? I know FH is future husband..but what is FI and FD (I think I also saw that)???

Also, when you send someone forum mail, do they get a message in their regular email saying they have li wedding mail? Or do you have to check it all the time?? Because I see a lot of people making threads saying..'Bridewhatever, you have FM'!

Thanks!