> Is there official documentation about what `str` (without an ampersand) is? For example, documentation [1] says that `str` is a "string slice" (without explai

> Is there official documentation about what `str` (without an ampersand) is? For example, documentation [1] says that `str` is a "string slice" (without explaining what "string slice" mean), and then goes on with description of &str. A `str` is really just a `[u8]` with extra semantics. Thus, a `&str` is really a `&[u8]`, a `&mut str` is a `&mut [u8]`, a `Box<str>` is a `Box<[u8]>`, etc. So we call it a "string slice", since it mostly acts like a regular `[T]` slice. In general, the term "slice" can either refer to the unsized type `[T]` or the reference `&[T]`/`&mut [T]` interchangeably. You could also call the latter a "slice reference" where the distinction is important; e.g., a `Box<[T]>` would be a "boxed slice", while `Box<&[T]>` would be a "boxed slice reference" or "boxed reference to a slice". But most of the time, the correct meaning can be inferred from context. > Also, I wonder, what do square brackets mean when they are used without an ampersand (as s[0..2] instead of &s[0..2])? `s[0..2]` is a place expression that refers to the raw `str` subslice. But since `str` is an unsized type [0], it cannot appear on its own; it must appear behind some reference type. Thus, `&s[0..2]` creates a `&str`, and `&mut s[0..2]` creates a `&mut str`. However, the ampersand isn't always necessary: you can write `s[0..2].to_owned()` to use the `str` as a method receiver, which implicitly creates a reference. [0] https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait https://doc.rust-lang.org/book/ch19-04-advanced-types.html#d...