Beginner copyright question

I am a YouTube beginner and am just starting to set up my YouTube channel. I also have a video in progress with an editor and would like to play a certain song during the video and have a basic question about the whole copyright issue.

I am of course aware that I am not allowed to use just any songs for my videos and that this could lead to problems. But how exactly is that? The editor said that its no problem, he edits videos for many people who use copyright songs in the video and then it is “only” not possible to earn money with them or not to monitize them (which is not my priority for the time being and therefore not a problem). But is it really just that? or will my video be restricted in some other way in terms of reach or something else? As I mentioned, I don't want to earn money with it yet, but of course I want to build up reach and not be limited in terms of reach. Could you explain this to me?