Alley: One lane wide. Alleys are usually access roads that run between city blocks. They are mostly named the same name as the street just before it. Alleys in cities allow garbage trucks or moving vans to operate without hindering traffic. Seattle is full of them.
Avenue: One of the more specific names given to a road, especially within city limits. Avenue might denote some sort of aesthetically pleasing design, but more often not.
Boulevard: Boulevards have a very pleasing aesthetic design to them, such as being divided with trees running down the middle. Boulevards have at least two to three lanes of traffic in each direction, and alot of times are highways that proceed through cities.
Drive: Much nicer than an avenue, drives are aesthetically pleasing, tend to not be straight, and contain nice homes. Most of the names (at least around here) are descriptive: Brookside Dr., Marine Dr., Foothill Dr.
Driveway: More comic relief than actual info, but some people name their driveways. Obviously, this is a country thing because the driveways can be a half mile long. They are not actually given the driveway designation, but road.
Grade: There is only one example of this in the Portland area. I'm not clear on the meaning of Grade as a designation, but I do know that Kings Grade goes through the Chehalem Mountains. My guess is that grade means a road that traverses a respectable slope.
Lane: Again, a more specific name given to a road. Lanes are generally narrower than avenues or streets, and have a tendency to not be so straight. The suffix lane may also be given to a half-block street.
Parkway: One of the rarer designations, Parkways are lovely little drives, often times through cities when the city decides that they need to spruce up the way the city looks. Parkways are very similar to Boulevards, but generally not as large.
Path: Get your 4x4! Paths are smaller than trails, mostly primitive roads, hardly ever paved. In fact, path is used more frequently for pedestrian traffic instead of automobile.
Road: (In my mind) the simplest element of land travel. Does it connect two points? Yes! Let's call it a road. Most any connecting land surface is named a road, unless it can be defined as something else. Sometimes roads will continue into cities and change into a street or something else. Other times, they will get wider and become a highway.
Run: This is about the rarest designation I have seen. In the Portland area, there is a Quail Run outside of Gaston in the Chehalem Mountains. I haven't actually seen this road, but I imagine it's barely distinguishable.
Street: One of the more specific names given to a road that is within city limits. Streets are generally paved and more straight then not. They are practically the same as avenues.
Terrace: Terraces contain very nice homes, and alot of times are on the sides of hills. Terraces are generally short and narrow, very reminiscient of a European backroad.
Trail: One of the more rarer designations, trails are generally private roads named for the estate or family of the property that they go to. In some instances, trail is used in conjunction with other designations (ex. Barlow Trail Rd., Logie Trail Rd.).
Way: This is very similar to a lane, although ways tend to be named for where they lead (ex. Rivercoast Way).