Can I use the Peleng 8mm fisheye lens with my Nikon D5100?

I've seen that it has an adaptor for Nikon but I'm not even completely sure what that means? I'm guessing that because it's an adaptor the shutter speed and aperture are controlled on the lens, rather than through my cameras controls?

I really want a fisheye lens, but for cheaper than what Nikkor offers, and something that isn't just a lens filter… So if this isn't compatible then something that is would be much appreciated. Please, & thank you!

This Nikon is my first DSLR so excuse the questions if they're silly!

Some adaptors pass the controls through, some do not. I would ask them before I bought. Fisheye lenses are not inexpensive and those that are, are cheap. Suggest you read some reviews before you invest your money.

This is the link I found.

It shows that the lens is made specifically for Nikon cameras, NO adapter is necessary

http://peleng8.com/peleng-8mm-nikon/peleng-nikon-peleng-8mm-f3.5-fisheye-lens-for-nikon.html

Since there's tremendous depth of field with a fisheye, there's really no need for auto-focus. Just set the camera to a hyper-focal distance that includes your subject and stop down two or three stops.