A broadcast is a transmission of a program to many people at the same time. The program is the show and the broadcast is the time when it's transmitted. So a single program (show) could be broadcast (transmitted) several times. The image shows a single program that was broadcast twice. Programs aren't always broadcast. Some programs are available online only, so they don't have a scheduled time. These shows are 'streamed' rather than broadcast.

"Program" means a planned, structured show. "Broadcast" refers specifically to the act of transmitting something, e.g. "over the air" by radio, where thousands of people can listen to it or watch it. Suppose a college orchestra performs several pieces of music in an auditorium. Suppose the only people who can see and hear it are the people sitting in the auditorium. That is a "program," but it is not a "broadcast." Now suppose it is the Boston Symphony Orchestra performing at Tanglewood. Suppose it is broadcast live on the radio by radio station WCRB at 102.5 FM. That is a "program," and it is also a "broadcast." Suppose a state park points a webcam at an eagle's nest and carries the video image live over the Internet. That is a "broadcast." I would not call it a "program" because there's no fixed schedule, and the eagles aren't performing or presenting. The name "broadcast" refers to the fact that the transmission is going out to everybody. When I call you on a mobile phone, I am using "radio," but I am not broadcasting because only one person, you, receives it.