When you move to a new page in a web browser, the previous open page is usually ejected from the computer's memory. Cached images and other data may have been saved, but most pages need to be loaded by the browser. Google Chrome developers are experimenting with a new "back / forward" cache to load the previous page.
Simply by clicking on the link on the page, this feature will keep the original page in the frozen memory. If you press back, the frozen page is immediately restored. The Chrome team estimates that in the Android version it could "improve performance by up to 19% of all navigation".
It is worth noting that Chrome is far from the only browser to experiment with this concept. Firefox has to some extent used the back / forward cache since Firefox 1.5 (released in 2005), but it seems to have been disabled for HTTPS sites. Safari has also changed since 2009.
This function is still at an early stage and there are still safety and compatibility issues. At least it's great for the absurd RAM volumes that are now on many Android flags.