Stage 6.12: Explicit Lifetimes
Even though Rust doesn't always show it in code, the compiler understands the lifetime of every variable and will attempt to validate that a reference never exists longer than its owner.
Functions can be explicit by parameterizing the function signature with symbols that help identify which parameters and return values share the same lifetime.
Lifetime specifiers always start with a ', e.g. 'a, 'b
Further information: