So basically, a pixel bot will hook into your game and grab your screen (this is why Overwatch applied something called screen-locking but it's bypassed now anyway). It'll scan your screen for certain pixels (normally health bars) and then draw a hitbox where it then aims inside of. Memory...
First of all, I'm rather new to the Overwatch cheating scene, so take this all with a grain of salt as I may have rose tinted glasses when it comes to Entropia.