These are sponsored by one of the other websites (our competition). I'll admit to attending them. One stood out because it was last year on the maiden voyage of the Freedom Of The Seas and I was hooked up with a memorable group of cruisers. The Captain showed up for this one. Captains normally do not show up for them. But we had some clout and he appeared.
RCI provides coffee and fruit punch, and some cookies. Someone from the cruise staff will thank everyone for coming and then another staff member will take the microphone and implore everyone to book another cruise while still aboard the ship. While that last part is not a bad idea since you get a $100 credit for booking another cruise while on one, one doesn't need to attend the meet and mingle party to garner this reward.
They last about an hour, not much more. It is a chance to meet other people you "met" online but have never really seen in person, of course these being people from "that other website"