API Software? Offtopic

Hello everyone,

this is just a off topic question to xibo. But i hope anyone can help me here.
In the API Manual, Postman is used. But now i wanna know what is Postman. You can “communicate” with the xibo api with postman. But how does these software kinds are called?

It’s API testing application, simple as that, I don’t think there is more sophisticated name for it.