String in rust is roughly like this in C: // NB: Must be utf-8! struct string { size_t sz; size_t capacity; unsigned char *buffer; }; &Strin

String in rust is roughly like this in C: // NB: Must be utf-8! struct string { size_t sz; size_t capacity; unsigned char *buffer; }; &String in Rust is roughly like `const struct string *`. str in Rust is just an array of (guaranteed utf-8) unsigned bytes. It does not have a capacity, so it can't be resized. You can't directly construct one (on the stack), because its size is undetermined and Rust doesn't have dynamic-sized stack allocation. &str, and Box<str>, are pointers to str, along with a size, and are roughly like this C: // NOTE: Must be utf-8! struct str_ptr { size_t sz; unsigned char *buffer; } The difference between &str and Box<str> is that the latter is an owned pointer to a heap allocation which will be freed when it goes out of scope. &str is unowned and might point anywhere: to a Box<str> on the heap, to a String on the heap, or to read-only static memory. IMO, it's probably easier to first try to understand the difference between `Vec<u8>`, `&[u8]`, and `&Vec<u8>`, because they are slightly less "weird" than the string types: they aren't syntactically special like `str` is[1], and they don't have an implicit requirement to be utf8 that is inexpressible in the type system. [1]: `str` is syntactically special because it is basically a slice, but isn't written in slice notation.