
The degree symbol is used for angles and arcs, temperatures, and the ‘proof’ of alcohol, among other things. You’ll even find it in harmonics. It started as a raised glyph of the digit 0, but best practice in typesetting and design now is to use a true degree symbol designed for the purpose.
The degree symbol is preferred because many fonts style the alternatives in ways that make them look very out of place as a degree symbol.