character-properties are a set of attributes supplied by the Unicode Standard. For each character contained in it, many properties are specified in relation to processes or algorithms that interpret them, in order to implement the character behavior.
The Unicode Standard, on top of defining the encoding of characters, also associates a rich set of semantics with each encoded character—properties that are required for interoperability and correct behavior in implementations, as well as for Unicode conformance. These semantics are cataloged in the Unicode Character Database (UCD), a collection of data files which contain the Unicode character code points and character names.
More information can be found on Wikipedia, in the official Unicode Standard as well as in this Unicode Technical Report.
