I just ZRH'd it, and it makes sense.
A Lanai is, essentially, a living room/family room style room but with screened walls. It's basically an upgraded porch/patio that allows you a family room but outdoors. It's typically larger than a porch, and screened in unlike a patio, and has furniture beyond just normal 'outdoor' stuff. It's mostly used in the tropics as people in colder climates just straight up wouldn't have a need for a room like that.
So there it is.
-DEAD-