Ownership, borrowing and lifetimes

Ownership is what makes Rust different, so give it real time. Every value has exactly one owner, and the value is freed when its owner goes out of scope. Assigning a String to another variable moves it, and the old name can no longer be used.

To use a value without taking it, you borrow it with a reference. You can have many shared references (&T) or one mutable reference (&mut T), but never both at once. The borrow checker, part of the compiler, enforces these rules.

That is how Rust prevents use-after-free bugs and data races without a garbage collector. Lifetimes are how the compiler proves a reference never outlives the value it points to.