Code unit size of 8-bit, 16-bit and 32-bit.

The Maximal bytes/character is 4 for all of the above but the Minimal bytes/character are respectively 1, 2 and 4.

UTF-8 is most common on the web. UTF-16 is used by Java and Windows. UTF-32 is used by various Unix systems. The conversions between all of them are algorithmically based, fast and lossless. This makes it easy to support data input or output in multiple formats, while using a particular UTF for internal storage or processing.

For further details and information:
http://en.wikipedia.org/wiki/UTF-8
http://en.wikipedia.org/wiki/UTF-16
http://unicode.org/
http://www.utf-8.com/