You really should only explain something if it helps define the purpose of your story. Remember that the story is a piece of art, and as such it is to convey a feeling (or set of feelings) to the audience.
Things can change based on perspective. For example, in first person, Mark may go on and on about the "legs on that girl", because your trying to get the audience to understand that Mark is a "legs man" and a bit of "dog". In third person, you may only mention that Mark was staring at "that girls legs" for what seemed like hours. There's no reason to go into detail. In both cases, you got the point across. The "girl" and her legs may not even be a plot point beyond setting up "Mark" and his state of mind and attitudes.
There is often a desire to "geek out" on explanations. But it generally doesn't help the story too much. A famous example would be Star Wars and "midichlorians". We watched and loved the first three movies, with out knowing anything about midichlorians. "The force" was just a thing that did stuff. In episode 1, when it was explained into the story, it kinda sucked, it was a disappointment. It wasn't needed, and the story would have been better off (though some may disagree) if Qui Gon Jinn just said "The force is unusually strong with this one" and moved on.
Even the "dump" from The Matrix, helped set up the plot. It explained that the world was not what it seems, and that humans are D-Cell batteries. That "the machines" are the enemies. All important parts. By contrast the "Architect Speech" is often thought of as one of the worst parts of the trilogy. We were much happier when Neo just did awesome action things, without having to get into the mechanics of why. Agent Smith was Neo's enemy, that was good enough, we didn't need more.
In The Wheel of Time Series, there is "The one power", we don't know how it works. It comes from the "good guys" part of the "source". We know there is a Male part, and a Female part. We know about differences between both parts. But we never really get the full picture. The glimpses we do get either further the plot (Men go crazy, Women don't. Rand has to teach him-self, kinda.) or serve to highlight one of the main themes of the story (Men and women are different). By that same token, I don't remember there being a sex scene with Matt in the entire series (maybe with the queen, but I don't think so), but you certainly know he likes the ladies, and likes getting into trouble with them.
So, the point is, unless your are making a point, or furthering a plot. Let the magic be magic. No one know how Harry Potter magic works other then is has something to do with wands some times, or words other times, and either you got it or you don't.