Managers coordinate all the teams in tech, marketing, sales, operations, support and other teams. They make sure that the teams focus on the important goals, strategies, measurements, etc. so that there is QoQ improvement.
Project managers handle 1 or more projects.
Program managers handle entire programs, each of which can contain multiple projects.
Product managers handle entire products, which can contain multiple programs.
Source: I'm a software Engineer who was promoted into a managerial position and hates it. I still prefer backend and software architecture.