My old man is a mason and from what I've experienced it appears to be a fairly pretentious, esoteric group of older men, who gather together to wear some rather odd attire, recite verses amongst various other things. More sort of an old boys club.
They do a lot of charity work and do look out for each other, for instance in times of poor health etc. I think they helped the widow of one of the members quite considerably recently when he passed on.
I've been asked to join, moreso prompted from some of the friends he has than my Dad himself, but I see nothing in it for me and my Dad himself admitted that there's little in it for me.
If i'm honest I've been to one of the ladies' nights (no sniggering motors boys) where they basically hold tribute to their wives and daughters, and it was all black tie and that, and whereas it was perfectly pleasant and all that, it was a very pretentious affair with deep belly laughing all round.
Ultimately something I'd never feel comfortable participating in or being part of.