A it short, a program comprises of

A project is a temporary accountability/undertaking to create something new – sometimes products or services. A project will have a definite start time, end time and also a set of specific objectives, which once attained the project is said to be completed. A program, on the other hand, is simply a group of all the related projects managed in a coordinated way so as to benefit which will not be otherwise available from managing the projects individually.
Also, a program may also include some other operations of the organization. To cut it short, a program comprises of multiple projects and is created to obtain broad organizational or technical objectives.
Examples:
Suppose a bank wants to achieve the target of being fully digital for all of its retail banking customers. The Bank will come up with a set or program which clearly includes an overall blanket objective that we want to be digital. Now, to do that we start with a number of small projects or simply a number of projects. These projects could include revamping the website, upgrading the mobile app, and so on. So now all the projects will have a certain objective that include start time and also the end time which would be clearly defined. Thus, every single thing that is done as a part of the program is what will build the project and overall projects as a group are programs.