This is a Katy Perry megamix, by Tommie Sunshine, and it's one of the bonus tracks from Teenage Dream: The Complete Confection. It contains every Katy Perry single from the Teenage Dream era.
In other words, this is the aural equivalent of gobbling down a pinata-ful of sugar, or perhaps eating five of those cakes with pies baked in the middle. ("Cakes with pies baked in the middle," incidentally, is a phrase that, had someone mentioned it to Katy two years ago, would be turned into a tour costume.) Or if you're sick of confection metaphors, it's the sort of thing scientists will dig out of someone's barely-functioning hard drive in 2020 and learn a lot about last year's pop, then promptly die because their modern body systems can't handle the sugar rush. Fortunately, that won't happen to you. Will it?