If you were to stand directly behind or in front of one of your tires to view its vertical angle, you would be looking at its camber. Actually, camber is most often set between 0 and -2 degrees, so you'd be hard pressed to see any lean at all. Negative camber refers to a wheel that is leaning inward with its top closer to the vehicle than its bottom. Positive camber, surprise-surprise, is the opposite, and means that a wheel leans out with its top further from the vehicle than its bottom. Many of the original Volkswagen Beetles had noticeable negative camber in the rear tires which made them look like they were squatting all of the time. A slight amount of negative camber setting is desirable because as a vehicle turns the outside wheels get pushed into a more positive camber state. This results in a camber of zero, or a straight up-and-down wheel, while cornering, which provides the largest contact patch and the greatest traction for handling.
Picture yourself hanging from an engine hoist directly over the front axle of your vehicle. Now imagine you've got X-ray vision and, for now at least, you're going to look through your car's hood and fenders to see the front wheels (there will be time to look through people's clothes later). At this point, you would be seeing the measurement of toe in your front-end. Toe is the angle of two wheels on the same axle, in relation to each other. For instance, if your front tires both pointed directly straight ahead and were parallel to each other, you would have zero toe. If the front of the tires were closer together than the rear, this would be toe-in, and if the rear were closer than the front, toe-out. Toe plays a major role in how a car feels going through a corner with toe-in creating more understeer and toe-out increasing oversteer. This is also where gas mileage can be improved since a vehicle with too much toe will be creating excessive friction and using up fuel (and tires) faster than it should. Toe settings vary from car to car and are determined by many factors including drivetrain layout and vehicle design.