discreet charges are individual particles with charge. In reality all charge is discreet because we can't divide an electron or proton into smaller charge. Continuous charge is an approximation we can sometimes make when we don't examine a charged object too closely. In this picture the charge can be seen to completely cover an area. If you imagine continuous charge as an image on your computer, then discreet charges are the pixels. From far away the image looks like real life, but they are really small dots, close together.
