What are emotes? - Emotes, or emojis, are small pictures that can be posted in chatrooms that have a wide variety of uses, but are typically used to describe a mood or reaction. 

Custom emotes can be used across a lot of platforms, but are found most on Discord and Twitch.

What are stickers? - Stickers are similar to emotes, but of a much larger size. They can fit a lot more detail (including text) and can show more of the character.

They are typically used in apps such as Discord and Telegram. Less platforms support custom stickers, so make sure the one you're using do!