Questions about HTML CSS. I don't know if there's anyone like this

I always feel that when I practice by making html or css on a practice pc, I modify it when I practice, and when I go into 127.0.0.1/xxx, it changes well, but if I go into my IP x.x.x, I can't modify it. What's wrong with this?

Sometimes, it's fixed on my IP, but it's not fixed on the back loop IP I don't know the principle.