Reference: PMBOK, pmstudycircle.com
Project: A project is a temporary endeavor undertaken to create a unique product, service or result. Projects cease once their objective is achieved.
Project management: Project management is the application of knowledge, skills, tools and techniques that helps projects achieve their objectives.
Program: A program is a group of related or similar projects managed in a coordinated way to get the benefits and control not available from managing them individually -- program has multiple projects that are similar, closely related.
Program Management: program management is the centralized, coordinated management of a program (inter-related, interdependent projects) to achieve its strategic objectives. Program management strives to:
1. Optimize resource utilization
2. Reduce friction or constraints between projects in program
Portfolio: is a group of related or non-related projects, programs. Portfolio may consist of multiple programs, or "multiple projects with no program at all".
Portfolio Management: is the centralized management of a portfolio to identify, prioritize, and authorize the projects or programs. (Based on organizational strategy, business objectives). Portfolio Management does not oversee any individual project or program.
