How to load only the content area, skip header and footer loading again in new pages over clicking links

Im using Basecamp, and when I click on the menu links, it just loads the inner body content alone, but still the URL changes, I wonder, Ive examined in network tab, and I see there for each link click it triggers an request and it only gets body part, no headers/footer are loading, amazed with the flow.

Where as in other sites(even in stackoverflow) it loads the page from the beginning, but with cache or some other stuff it loads quickly but there is a lil flicker if we could examine clearly.

Do you guys have any idea how it works, are there any frameworks that helps this way? because this really works extremely fast and no flicker at all in header menus, and specially while browsing in mobile it gives a feel like using an application(mobile app that loads just the content)

Please let me if you have any idea how this flow works.

Thanks in advance