Good news, World of Warcraft time warriors extraordinaire: With the upcoming patch 10.1.5, you will not be going back in time. You will, instead, be visiting alternate timelines! So it’s more like Chrono Cross than Chrono Trigger. Mostly because of the parallel timelines, but maybe also because the plot will make zero sense and will end with you fighting your evil time-traveling father-clone in a cat-man’s body. It wouldn’t be the worst story twist the game has had, we did go through Shadowlands. Anyhow, you can get up to speed on the whole thing with the official previews.
The short version? You pop into parallel versions of Azeroth that remind you of the good ol’ days before the dark times, represent other possible futures, invite you take on tasks, and allow you to earn a new sort of currency that you can trade for cosmetics and gear. Wowhead already has information on what you can purchase in exchange for Paracausal Fragments, so if you need additional motivation for exploring the Murloc Timeline, there you go.