It describes it fairly well and compares it to the old (and now redundant) reduced PSM effect of Sport Plus found on older Macans.
PSM Sport was introduced into the range since the latest 991.2, Macan since the GTS and the 718, so long as they have Sport Chrono.
Without copying the entire article, the best summary I can come up with is that it's more or less PSM off, but with slowed oversteer yaw impulses and if it feels you are in control, it lets you get on with it, otherwise, clamps down for safety. PSM is fully enabled if you breach the ABS threshold on the brakes (again, safety).
Also, it's said it's not a "drift button" as that takes away any kind of driver involvement.
