In the US, the terms tend to depend on which geographical area you are in. In the southwest US, a condo is typically an apartment that is purchased rather than rented. A condo can have a garage though, so it depends on the particular construction of it, and there's typically a pool and community building. It depends on how the homeowners association has been setup in terms of ownership of the surrounding land and who is responsible if something breaks (HOA versus owner).
If you have 2 houses joined together and only share one wall, that would be a twin home. You don't often hear the term duplex but some people do use it for twin homes. I live in a twin house and it was built in the 70s and overlooks a large canyon - it's very easy to hear your neighbors or smell their cigarette smoke because the canyon reverberates the noises people make.
If you have houses sharing all walls, then it's usually a patio home or a town home, and they're usually built in a community surrounding parks or golf courses. A house that's been separated into rental units is now called "hacked" - a relatively newer term for that, and not always legal.
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