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Traffic can refer to people or information.
When referring to people, traffic is the result of a whole lot of people simultaneously deciding that they'd all really rather be somewhere else. When you get enough vehicles in one place (in this case automobiles), it almost inevitably produces a traffic jam (which is not nearly as pleasant as the strawberry jam you put on your toast). In this case it would probably be faster to get out and walk, and is yet another example of the all-too-common phenomenon wherein humans profess to hate something despite the fact that they themselves are causing it. Other examples include pollution, governments, and daytime talk shows. Watch out for rednecks pulling out guns in traffic jams, a phenomenon known as road rage.
The traffic of information is much the same as traffic of people, only the information moves through wires, fibre optics, or satellite signals. Information traffic jams can also produce high levels of stress and irritability, but you usually don't have to worry about rednecks pulling out a shotgun when your computer is too slow.