Basically, after working with lifetimes for so long we realized that a great many functions that take lifetime parameters follow a similar and straightforward pattern. As of this release, we now allow you to omit lifetime parameters entirely for functions that follow this pattern, which is likely the vast majority of functions in your code that previously required such annotations.

The detailed release notes have a more, er, detailed explanation: https://github.com/rust-lang/rust/wiki/Doc-detailed-release-...