Physical custody is like a game of tag. When you have physical custody of something, you are "it" and responsible for taking care of that thing.
When it comes to kids, physical custody means that one parent (or another trusted adult) gets to spend time with the child and take care of them on a regular basis. This might mean that the child lives with that parent most of the time, or spends weekends or holidays with them.
Sometimes, parents might share physical custody and take turns being "it." This is called joint physical custody.
It's important for parents to figure out a custody arrangement that works best for everyone involved, including the parents and the child. The most important thing is that the child feels safe, loved, and cared for by both parents.