Buy mode

Buy Mode is one of three modes in the game (the others being Live mode and Build mode) in which you may purchase and arrange any of the objects on the current lot. Construction-related elements such as doors, windows, fences, and stairs are not associated with Buy Mode, but are in Build Mode. Buy Mode largely focuses on furniture and appliances.

Related
The furniture is really not the way to categorize buy mode. It in truth holds many more things including a skating rink and a rollorblading rink. It can also be confirmed in the kids zone of miscelaneous bearing teddy bears. Even though anything in build or Buy Mode is for buying. Build is different in the sense that you have to build it onto your lot.

Buy mode objects
Objects can be grouped by function or by room.

Plumbing
Toilets, sinks, showers and bathtubs.

Sims mainly use these to fill their Bladder or Hygiene needs

Most of these require cleaning. They might also break down, requiring repairs.

Appliances
Mainly kitchen objects: Refrigerators, stoves and dishwashers.

Comfort
Beds, chairs, armchairs, sofas, bar stools and deck chairs.

Surfaces
Benches, kitchen tables, desks, side tables etc.

Electronics
TV sets, Computers, sound devices, phones etc.

Decorations
Mirrors, Plants, paintings etc.

Mainly for improving environment, but some offer interactions.

In contrast to most buy mode objects, many decoration objects keep their value throughout the game.

Hobbies
Telescopes, chessboards, bookshelves, etc.

Vehicles
Cars and bicycles.