What does AL in Nikon lenses mean?

Can use a lens like http://www.ebay.ca/...0917183776 on my Nikon D90?

Actually it is AI (Auto-Indexing)

There are manually focused lenses from the 1970's

Your D90 needs Nikkor lenses that are AF, AF-I or AF-S or generic lenses that are auto-focus

NOTE: "This is a Vivitar matched teleconverter for the 70-150mm telephoto made for Vivitar by Kiron". That means that you would also need the 70-150 mm Vivitar lens as well as a camera like the Nikon F2, F3, or F4 to make it all work together

AL is a Pentax thing, not Nikon.

After checking your link, those are the letters A and I, not L.AI lenses are manual focus lenses that include a coupler between the lens aperture ring and camera body. Here is the direct explanation of this feature from Nikon: http://support.nikonusa.com/...ai-lens%3F

The answer is yes, although you will lose all electronic connections to any AF lenses. That means no aperture control on G lenses, and no autofocus at all.

As ace said, this is a teleconverter. Pretty much useless unless you also have the lens that matches it.