As with any browser, Chrome lets you browse the Web via multiple tabs. Loading select pages in background tabs would mean the browser will not have to load those pages from scratch when they're needed by the user, which will make them available much more quickly. How this will be executed isn't clear yet. Google won't be able to take up too much memory with background tabs or the speed benefits will quickly fall apart. Furthermore, Google will need to choose which pages to preload among the hundreds of thousands a user might want to visit, and how long it will keep them cached.
Google has an obsession with speed that many have benefitted from. It is one of the primary reasons why Chrome's market share continues to grow at a steady rate. Nevertheless, we're going to reserve judgment until we see this feature for ourselves. The idea is an interesting one, but as always, it all comes down to execution.