Project work is different from “regular” work or operational work. A person who works for, let’s say, an insurance company generally engages in daily operational work, which means that each day they engage in the work necessary to collect payments from customers, answer customer inquiries, and other daily tasks that are the business of the insurance company. However, project work has a defined beginning, middle, and end. Project work doesn’t continue day after day after day with no end. So, the term project life cycle is really just a fancy way to refer to the beginning middle and end. Typically, the project lifecycle has five phases: initiating, planning, executing, monitoring, and closing.

Found this: "A project life cycle is the sequence of phases that a project goes through from its initiation to its closure." From: https://www.invensislearning.com/articles/pmp/what-is-project-life-cycle-and-its-main-characteristics I hope this helps!

If you Google "project life cycle" you will find lots of information. If you want to know about formal standards (i.e., those met by Certified Project Managers), then pay attention to the reference to, by, and from the Project Management Institute (PMI).