What are the differences between Rust's `String` and `str`?

Question

Why does Rust have String and str? What are the differences between String and str? When does one use String

Answer 1

For C# and Java people:

• Rust' String === StringBuilder
• Rust's &str === (immutable) string

I like to think of a &str as a view on a string, like an interned string in Java / C# where you can't change it, only create a new one.