To put it very simply, it sort of provides a way to make everything 'static, except for it's actually arena's lifetime, 'a. So you no longer care who outlives w

To put it very simply, it sort of provides a way to make everything 'static, except for it's actually arena's lifetime, 'a. So you no longer care who outlives who because all the objects will die together when the arena dies. And you're dealing with simple references, &, and not some wrappers.