What is UTF-8 encoding?

Computers only store numbers (bits → bytes). There is no built‑in “A” or “😀”; we need a rule that says: “this number = this character.” That rule is an encoding. UTF-8 is one such rule: it defines how characters are turned into bytes (and back). Today, the vast majority of websites use UTF-8 for their pages and APIs. So yes: UTF-8 is the “rule” that tells us how to convert between “raw” byte sequences and specific characters (and the other way around).

when we agree to use UTF-8, we use that rule to convert between bytes and characters.

Idea as “binary (bytes) ↔ character via a rule,” and that rule is UTF-8.