OK let’s do this: Custom emojis.

A weird thing about   is that each 💻 (server) has its own list of custom #emoji, which are represented in messages by a colon-bracketed ‘short code’, like this:  

But that shortcode can only be used by *you* if it exists on your server – you can 👁️ custom emoji in 💬 from other servers, but you can’t use them.

There’s too many servers to list their repertoires, and some have hundreds. But this one stood out – mathstodon.xyz: 😆