b4035917_roject__Program__and_Portfolio__Portfolio
[Characteristic] Definition [Project] A limited set of efforts (work) to create a unique product, service, or results. [Program] A group of related projects and possibly some related work that does not belong to any project. [Portfolio] 
A collection of projects, programs, and other related work.
Become a Certified Project Manager: Chapter 13: Relationship between Project, Program, and Portfolio
Portfolio