Excerpts from http://ijstokes.paunix.org/unicode/unicode.html

Some Acronyms:

UCS(ISO 10646-1): Universal Character Set
BMP: Basic Multilingual Plane
UTF: Unicode Transformation Format
UTF-8: 8-bit Unicode Transformation Format

UCS is from ISO, Unicode is from Unicode consortium.
In 1991 they agreed to collaborate and from then on,
both standards are essentially same. But both organisations
publish the statndards individually. They coordinate any changes to standards.

UCS/Unicode is 31-bit character set [...]