What is the difference between a project, a program, and a portfolio?

A project is a temporary endeavor to create a unique product, service, or result, with a defined beginning and end. A program is a group of related projects, subsidiary programs, and program activities managed in a coordinated way to obtain benefits not available from managing them individually, such as a company-wide digital transformation. A portfolio is a collection of projects, programs, and operations managed as a group to achieve strategic objectives, such as all IT investments in an organization.