Unicode is a 16-bit character encoding standard and is capable to represent almost every character of well-known languages of the world.
Before Unicode, there were multiple standards to represent character encoding −
ASCII - for the United States.
ISO 8859-1 for Western European Language.
KOI-8 for Russian.
GB18030 and BIG-5 for Chinese.
So to support multinational application codes, some character was using single byte, some two. An even same code may represent a different character in one language and may represent other characters in another language.
To overcome above shortcoming, the unicode system was developed where each character is represented by 2 bytes.