What is Rally?

Rally (Rallying, Stage Rally, Rally Racing, ProRally) is a motorsport where a driver and navigator (co-driver) race down closed dirt roads, one car at a time, as fast as they can. The cars race against the clock and not head-to-head. The racing sections are called Special Stages and are closed to all non-rally traffic. They will be anywhere from 5 to 20 miles or more. Teams are timed and are given a time card that will be checked throughout the race. When not on a Special Stage the teams Transit between Rally HQ, Service, and the Special Stages at normal road speed, obeying all traffic laws and speed limits. One, two, or even three day events will run anywhere from 30 to 200+ miles of stages with overnight stops. Rally is an international sport that has had some success and is gaining popularity in the United States.

The Driver: Rally drivers are usually regarded as the best drivers in the world as they drive on tarmac, gravel, mud, snow, and ice – in all seasons and conditions throughout a championship. They often use advanced driving techniques such as left foot braking and lift-off throttle steering. The driver listens to the co-driver on an in-car intercom system.

The Co-Driver: Rally co-drivers have an equal part in getting the car to the end of rally. They read the route book, the stage notes, and any pace notes telling the driver not only where to go, but usually every turn on the Special Stage. Because of the extraordinary amount of information, special abbreviations that both the driver and co-driver understand are used.
For Example: R5>cr 100 ! L2
Would be spoken: “Right Five Over Crest, One Hundred, Caution! Left Two”
Which means: There is an easy right turn over a crest in the road, and then in 100 yards the road will turn into a hard left.
For even MORE on notes look here.
On top of that, the co-drivers are making sure that the team checks in at all time controls on the route on time. These calculations are done with the time card.

The cars: Street legal production cars. All cars must have a roll cage and top level safety equipment, which includes seats, helmets, belts, etc. Because they will be driving on public streets during the rally (during transits) they must be properly registered and insured. Depending on car class, they range from low power front wheel drive to turbocharged all-wheel drive cars. Production classes usually permit little to no modification to the engine. Open classes usually have no real engine restrictions. All cars are allowed suspension and tire upgrades.

The teams: Besides the driver and co-driver in the car, there is a group of individuals that make up the service crew. They wait patiently at the service location for the team to return from the special stages. The crew gets 20 to 45 (often frenzied) minutes to repair any damage that may have been done to the vehicle. Common service tasks include changing tires, checking suspension, tightening bolts, and refueling. Depending on the rally and the length of the stages this could happen several times, or the crew could have to move to a different location for a later service stop.

Summary: As you might imagine, rally is a fast and exciting sport that involves several disciplines. From the driver taking a fast line and driving the stages to the best of his ability, to the co-driver making sure the team arrives at the service area on time, and allow the service crew to check and fix the rally car. A lot of people are involved in a championship winning team. Rally is a lot of fun to do. Rally is great fun to watch! Check out the rallynotes.com channel on YouTube.
More info on wikipedia – Rallying.