What happens when charging and using MacBook at the same time?

So I have a question, What happens when you charge your MacBook while using it? I know that when only on battery, especially when doing heavy tasks, the battery drains quicker and can also overheat that can damage it and lower the battery health quicker. So, when I use it on power does the battery work at all? Does the power it gets first go to the battery and then from the battery to the Mac so it can work or it goes directly to the Mac so the battery isn't being used and is not overheated? Also, I saw that when battery is more than 93% it says it's not charging. Is this what I'm talking about?