Why should I clear my browser cache? I updated a page but can't see the changes

Why should I clear my browser cache? I updated a page but can't see the
changes

I updated my page and i can't see the changes if i won't clear my browser
cache . So, people were not seeing the change. Then the thought came that
they need to clear their cache. But how can I force a browser to clear its
cache when it visits my website?
It's urgent, help please :)