Ah, good question. They're similar but have some differences depending on where you use 'em.

"Notes" and "posts" are often used interchangeably to mean any kind of written content shared online - like a blog post or a note on Facebook.

A "tweet" is specifically a post made on Twitter, and it's limited to 280 characters.

So while they all involve sharing thoughts or info online, the main difference lies in where they're posted and how long they can be!