In casual conversation, people tend to use the terms "drifting" and "powersliding" pretty much interchangeably. It's especially common to call any sort of controlled oversteer a drift. But just because it's popular doesn't mean it's accurate. There actually is a technical difference between a powerslide and a drift.
In their latest YouTube video, do an excellent job of explaining and then illustrating this difference.
Essentially, a drift starts before the apex, while a powerslide starts after the apex. With a powerslide, you keep things tidy up until you hit the apex. Once there, you put the power down—which, in a rear-drive car with good power, can make the back end step out to varying degrees. In a drift, the slide starts much earlier. Your goal is to induce oversteer going into the corner, not on your way out—sometimes using a clutch kick or a tug on the handbrake to get the car sideways ahead of the apex. Any time you're oversteering before the apex, it's a drift.
So now you know. And next time one of your friends incorrectly calls a powerslide a drift, or vice versa, you'll be able to point out exactly how wrong they are.