All right, all writers will already know this; this is the final post in a series explaining some jargon I've been using. When you've got a book of short stories by one author, that is a collection. When there are multiple authors, that's an anthology, or an "antho". Anthologies range from really poor rip offs that pay nothing to the writers and sell no copies to very prestigious (that still don't pay a ton to the writers), such as the Year's Best anthologies edited by Gardner Dozois (Science Fiction) and Ellen Datlow, Kelly Link, and Gavin Grant (Fantasy and Horror). Big name authors can make decent money on their short stories because they will often be the selling point for the anthology.
There are two different kind of anthologies, invitation only, and well... there isn't a name for the other kind. They're the kind that anyone can send a story in to. (The Year's Best anthologies are a little different, because there all of the stories have been previously published, and thus are written well before the anthology selection begins.) The invitations for the invitation only ones can be quite coveted, especially if there is a big name author or two included. Invitations come in a few flavors: 1) a request for an already written story (happens if it's a famous story), 2) invitation and we'll buy anything you write (happens if you're a famous author) and 3) invitation and we'll consider what you've written. I have only ever qualified for this third kind, when I've qualified at all. My first pro sale was to an invitation only anthology in which it was advertized that only one unpublished author would get a slot. I'm not sure if that ended up being the case, but if it was, I was that unpublished author.
Anthologies nearly always have a theme. I.e. Alien Sex, random words from the National Spelling Bee finals (I'm serious), educational science fiction, etc. My first sale was to one on polar science. There have also been a few ethnic anthologies, i.e. Dark Matter, for black sf authors, Wandering Stars, for Jewish ones, etc. I was invited to the Chinese themed one, currently titled The Dragon and the Stars. We'll see if I manage to land a place in it. The word limit was 6,000, which is a stretch for me, because my natural length for a short story is 7,000-ish. But anyway, I wrote the best story I could and sent it in. Samantha Ling, one of my Clarion West classmates, submitted one as well, and we critted each other's. It would be very cool to share a table of contents with her, and with our classmate Susan Yi, who was also invited.
That, I hope, reads a little more clearly than my weeks' old post that confused some people on Facebook.