The concept of program refers specifically to the series, listing, or group of those similarly structured and or otherwise interrelated projects that when the decision is made to coordinate the management of all them in a coordinated way will garner benefits and improved ability to maintain control as opposed to if the management of each of these took place on a project by project basis. Some tangible examples of instances in which it is beneficial to group management of certain projects within the overall scope is when it comes to organization and maximum efficiency in regards to staffing. It is far more efficient to distribute staff across a number of independent projects yet within one umbrella program than to attempt to coordinate staffing across all projects independently. It also helps to better utilize office resources and other supply materials. Specific enumerated program elements may consist of not only large scope work-related items, but also in regards to elements outside of scope of the discrete projects that make up the program.
This term is defined in the 3rd and the 4th edition of the PMBOK.