What is the difference between lenses for a Digital SLR camera? I am looking at Nikon and tamron lenses?

I am going to be purchasing a Nikon D80 and I am looking at packages not sure if I should get one with Nikon lenses or can I go with off brand. And if I do go off brand which is the best/worst and your opinions.

A good lens is far more important than a good camera. Nikon makes some of the best lenses. That's why they cost more. I'd rather put a Nikon lens on an off-brand camera than an off-brand lens on a Nikon camera.

Not all lenses fit all cameras. Some cameras will only use their own lenses. Others can interchange and use other types of lenses,

Tamron make some really good lens's not sure what mount system the D80 uses as it is a new model, but I am sure Tamron will have a lens of the type you need at a lesser price than Nikon

Good one, Terisu. For some people, the most important reason to buy a Nikon camera is so you can use Nikon lenses. There are other lenses that are satisfactory, but it seems that the reviews ALWAYS say that it's "close" or "for the money" or something else to qualify the positive rating so that you understand it's not expected to be up to the Nikon standard.

Some Sigma or Tamron or Tokina lenses might match some Nikon lenses, but I think if you compare the 17-55 f/2.8 of one company vs. all the others, the Nikon will be the best, and so on. Compare the features as closely as you can instead of looking at an entry level Nikon lens and a premium level after-market lens.