What cosmetics are good for the skin barrier?

I didn't really use the word or expression "skin barrier" in the past, but at some point

I noticed that the term "skin barrier" is used a lot.

If the skin barrier breaks down, you get breakouts, your oil-moisture balance drops, and so on.

Does it just mean that if my skin gets worse, my skin barrier breaks down?

What are some good products for repairing the skin barrier?