The Aino House is a house in the Azabu-Juuban neighborhood that the four inner senshi--Mizuno Ami, Aino Minako, Hino Rei, and Kino Makoto--share. Also to be found in the residence are Xadium Prime, Minako's husband, and Artemis, everyone's favorite very sad cat.
Over the course of its existence, the Aino House has endured various degrees of separation from the Ten'ou House--sometimes existing as a wing of the latter, sometimes having its own more-or-less separate nature. Now that Makoto, Rei, and Ami are inhabiting the place, as well as Minako, Xadium, and Artemis, it seems to have branched off into its own much less dramatic place. Of course, they still keep in contact through the IRC--how could they not?
Details can be found at The House.