Elision Rules
When lifetimes are inferred.
Lifetimes You Do Not Write
Many functions take and return references without any lifetime annotations, yet they compile. That is because of lifetime elision: the compiler infers obvious lifetimes for you.
Elision Is Just a Shortcut
Elision does not remove lifetimes; the compiler still fills them in behind the scenes using a few deterministic rules. When the rules cover your case, you can omit the annotations.