If you ever want to restructure your site, one of the biggest issue is the already established inlinks and search engine rankings. You do not want to lose those, under any circumstances, but this does not mean you cannot move your pages.
When a user requests a page, their browser sends the request to your server. Your server will return a status code – this status code is 200 for a normal page. You may have also heard of 404, used for a non-existant page. You can redirect your users with a 302 redirect – this is a temporarily moved page, or a 301 redirect – a permanently moved page.