Unicode is a universal character encoding standard used to represent text from virtually every writing system in the world. Each character (letters, numbers, symbols, emojis) is assigned a unique code point (for example, U+0041 for "A"). Unicode encoding formats like UTF-8 and UTF-16 specify how these code points are stored as bytes.
Source: Encoding Transformations/README.md in PayloadsAllTheThings. From PayloadsAllTheThings by Swissky and contributors. MIT License, Copyright (c) 2019 Swissky.