Today I noticed two questions (here and here) on SF closed for the same reason, being off-topic. However, I noticed that one of them was put "on hold" as off-topic and the other was "closed" as off-topic.

That made me wonder, what is the actual difference between the two? They seem so similar, who/what decides whether or not a questions should be closed or put on hold? I hope anyone can clarify this, as I'm a bit puzzled about it.