It's a camera so you are looking at a digital picture.
The camera is quite sensitive so will allow you to 'see' a much clearer picture at dusk than you can with the naked eye and the, as the light fails, the camera switched to an IR sensitve mode and you get a black and white picture.
With IR illumination the picture is very clear, and you can easily 'see' in the pitch black of night.
Horses, cows and sheep as well as people cars, bulding and trees are easily identifyable out to several/nmany hundred meters. A rabbit or fox is clearly visible out to a couple of hundred meters. Eye-shine is visible well out but it's only until the animal is closer in (200 to 250M) that you can tell it's a fox and you'd likely need to to be closer than that to identify a dog from a vixen.
There are several vesions of these cameras out there.
The newer (more expensive) versions are better than the older due to advances in software and chip technology.
There is a lot of math that can be used to show that this one is better than that one.
At £300 the WULF is a bargain.
If you've not seen through a modern NV scope you will be amazed how clear they are.