Someone else has a server and their infrastructure is set up so you can upload a zip of some executable and they’ll figure out how to make it run. You don’t worry about any details except your code and whatever API is require to be compatible, and they worry about hosting it, making sure it has memory, CPU time, disk space, DB, etc.
Others have covered it but the API pricing was $12,000/50 million requests, which is absurd bordering on comical.