Unicode
From wikinotes
Unicode is a standard for text encoding.
It extends ASCII, which espresses english in the first 7-bits of an 8-bit integer.
In unicode, the 8th bit is used to change switch out sets of 128 characters.
When the first bit is 0, the character set is ascii - which conveniently means all ASCII is valid unicode.
Unicode can be represented using various different text encodings.
Documentation
wikipedia https://en.wikipedia.org/wiki/Unicode