Can I use that as a verb? Well, I’m going to anyway.
From what I’ve seen, it’s a social, semantically enabled, co-brandable information collecting & sharing service. Well, that makes it sound a lot more clinical than it really should. Picture something like Facebook+Digg+del.icio.us+flickr+blog+email+??. Only it’s smarter because, while allowing you to tag the content you want to share, it also extracts concepts and makes tagging suggestions. By “co-brandable” I mean that one can create different communities, and they’ll sort of stay distinct, but your profile can cross communities and mingle. Or something like that.
Honestly, there’s probably more to it that I’m not able to express. I requested an invite to the beta on Monday, but haven’t heard back yet. I’ll post more when I do and I’m able to try it out first hand.