1. A particular mapping between characters and byte strings, i.e. the combination of a particular character encoding (which maps between byte strings and integers) and a particular coded character set (which maps between integers and characters).
For example: ascii (the ASCII coded character set, encoded directly as single-byte values), or utf-8 (the Unicode coded character set, encoded with an 8-bit transformation method).
2. Occasionally: a character repertoire; or a coded character set.