I do not know everything about every computer language, or even every one I write about on this site. Instead, I learn as I go along. From other languages like C# I was familiar with the concept of enums—types that store known values and can be referenced by name.
But in Rust, enums have an additional feature—they are an algebraic data type. This means a value in an enum can reference some data—like a struct instance, a String, a tuple or a number.
In practice, this means we can use a single enum to refer to multiple data types:
So we can create a Color enum, and it could have a value of Red with a String, or a value of Blue with a usize instead. And we can refer the Color as meaning either Red or Blue—and a String or usize only in appropriate cases. This can simplify some programs where we must return many types of data from a single function.