“Basin tap” and “basin faucet” usually mean the same thing: the fixture on a basin/sink that controls water flow. The difference is mostly language and regional usage.
In British English, “tap” is the common term. So a basin tap is the water outlet fitted to a wash basin, usually in a bathroom or utility area.
In American English, “faucet” is the common term. So a basin faucet is the same kind of fixture, just using U.S. terminology.
If you want a more practical distinction, “basin tap” can sometimes imply a simpler, more traditional design, while “faucet” is used more broadly for all sink water controls, including modern mixer styles, single-handle units, and sensor taps. But technically, there is no real functional difference.
Also, “tap” is more commonly used for the hardware in UK, Ireland, India, Australia, and many Commonwealth countries, while “faucet” is standard in the U.S. and Canada.
So:
- Basin tap = British/commonwealth term
- Basin faucet = American term
- Function = essentially identical
In short, the difference is mainly vocabulary, not plumbing.