wide angle lens is technically lens below 50mm, which is considered 'normal' as it has the angle of view closest to humans. But on cropped body(which I presumed you have), it is perhaps below 30 or so so sony, nikon and canon, and 25 for olympus. Anyway, dont really worry about it, there isnt really strict category differences. The numbers are continuous right?
ND filters are neutral density filters usually used for landscape. They are transparent films you put infront of your lens, acting like sunglasses, but only on half the film. Usually used to cover the bright sky so you dont overexpose them, or underexpose your landscape. I am not sure about its uses in street photography.
CPL filters are circular polariser. The function is, well of course, to polarise light. It makes the colour more saturated by blocking reflections of light off metallic surfaces.
Common effects are like making clouds more detailed and ability to see through water rather than its reflection.
Actually all this can be found by googling.
Well, I can really see how some of the more experienced forum-mates gets frustrated over the number of posts asking about all these stuff.
cheers.