A group of objects that make life easier for your duplicates, without which it is difficult to work later on. Your first choice will usually be a simple cot. Thanks to which, not only will the duplicates have a place to sleep, but they will also avoid the negative sore back status. You can assign each bed to a specific colonist, the game does this automatically too. The mess table works quite similarly. It also affects the mood positively, the duplicates no longer have to eat on the floor. The tables are automatically assigned. The case is a bit different with massage tables. You decide when your duplicants can get a massage. This can be done by setting the maximum and minimum levels of stress that will allow the duplicants to use the tables. A duplicant will be chosen automatically, and he will use the table when he's got a free moment to spare. Additionally, a table needs to be plugged into the power grid. It's a key piece of furniture as one of the few things that can affect stress levels of your duplicants directly. Make sure you have enough tables as your colony expands and take care to decorate the rooms in which you put them.
Lighting also affects stress. Duplicates feel better if the room is well lit. The floor lamp gives light at a small distance around itself. The ceiling lamp illuminates most of the room if it is placed high enough. Lamps require electricity, which makes them a quite inefficient method of decorating, especially when compared to other objects that give more bonuses and do not need any electricity.