What is an emoji?

An emoji is a small picture — a face, a flag, a pizza slice — that is encoded as a text character by the Unicode Consortium. Because every emoji is really just a standard character (like the letter A), you can type them, copy them, search them and include them in any app that supports Unicode.

Each emoji is rendered by your device's font: Apple draws 😀 one way, Google draws it slightly differently, but the underlying character (U+1F600) is the same.