You can earn money through their website (searches, purchases, etc.) but the easiest and most passive way to earn is by running their various apps. They tend to be more android-oriented but they have some apps that also work on iOS devices.
People who make a lot of money with Perk are running multiple devices (you can have up to 5 per app) and they are running them constantly. They refer to them as Perk Farms. However, you need to be careful about bandwidth caps that your ISP might impose.
I have Comcast and they don't cap bandwidth.
I have several old smartphones (no phone number associated with them) running 3 different apps. I don't run apps on my personal cell phone. I redeemed twice this week for a total of $75 in
Amazon GCs. The week before, I redeemed for $100. The program can be buggy at times, but they consistently pay out on Mon.-Wed.-Fri.