UCS2 coded SMS contains 70 characters. It is in use in countries that needs more then the standard
7 / 8 bit to code their character set. Hard to understand and to explain, if you are born in a 7 / 8 bit country. UCS2 is 16 bit coded.
Latest Nokia phones use UCS2 to show short messages with blinking characters. More about blinking characters you will get at http://www.hut.fi/~ptuomine/nokia/software/flash-en.htm
The original description of the UCS2 you will get at http://www.iso.ch
http://www.unicode.org offers the specification free of charge.
More about that at you will find if you follow the LINK button in top menue.