What is a program?
A program is a group of related projects managed in a coordinated way. Lots of organizations run programs because they can accomplish multiple deliverables or output and have a set group of best practices that can be applied to all of them. Think about it this way. If you were building data centers at 15 locations, there are some standard approaches you would use at every location. This may include the process by which you order or transport materials, similar (if not the same) types of resources, and how you create your process flow charts. Even if you had 15 project managers working at each location, there are some best practices that are applicable across all projects.
You might be wondering how these projects could be considered unique since everything sounds the same, but remember you are at different locations.
Different stakeholders have different needs for their data storage, different thoughts about the final result, different risk events, and even different scopes of work. One data center could be much larger than another and have different configurations. All these items make each project unique, but similar enough that best practices and processes can be shared and implemented across the program.