Do I need to understand this myself first?

No. Every child-level explanation on this site is written so you can read it out loud with no preparation and it will make sense coming out of your mouth.

If a follow-up question arrives that you cannot answer, the best available response is the honest one: I do not know either, let us find out. That sentence teaches a research habit worth more than the original answer would have been.

The grown-up section under each explanation is there for your own curiosity. It is not homework and the child does not need it.