What is exactly a host club? Do they strive to excel in hosting parties, or things like that?

Hmm... Since Lunar dropped Bleach, I wonder if this is to be their new big thing, or is this just a smaller project. Or perhaps it's just an erroneous idea of mine that there should be always a mega series being subbed... Well, anyway, I'll wait a little to see the reactions here before deciding whether to try this one or not.