KOI8-R is an 8-bit character encoding, designed to cover Russian, which uses a Cyrillic alphabet. It also happens to cover Bulgarian, but has not been used for that purpose since CP1251 was accepted. A derivative encoding is KOI8-U, which adds Ukrainian characters.
Mac OS Roman is a character encoding primarily used by the classic Mac OS to represent text. It encodes 256 characters, the first 128 of which are identical to ASCII, with the remaining characters including mathematical symbols, diacritics, and additional punctuation marks.
The name LAME is a recursive acronym for "LAME Ain't an MP3 Encoder". Around mid-1998, Mike Cheng created LAME 1.0 as a set of modifications against the "8Hz-MP3" encoder source code. After some quality concerns raised by others, he decided to start again from scratch based on the "dist10" MPEG reference software sources.
A "character set" is a mapping of characters to their identifying code values. The character set most commonly used in computers today is Unicode, a global standard for character encoding. Internally, Windows applications use the UTF-16 implementation of Unicode.