One screen divided showing all4 pictures from 4 cameras. Later they can be seen one at a time,enlarged, all4 pictures get recorded. Some DVR's automatically erase stored info after a certain time period expires.
I really like the ones that have motion switches built in the cameras so recording dead air and then if someone has to spend their time looking over allthose hours... YEEgad!
Make sure and read and then think about what you will be needing as far as the cameras being weather -proof or not?
A very damp location or one with tempersture changes can sometimes condense drops of water on the lense negating most of or all of the picture.
I had to install some cameras low enough that some AzzWhole could jump up and smash his fist against them. I built a backing to mount the cameras to,they were pieces of 3.4 inch thick plywood about the sixe of a football, with long spikes driven through the wood making numerous sharp points to puncture any drunken vandals paws! The nails were not the least bit hidden and guess what? nobody punched any cameras! No blood stains either!