Ares I is another component of the Orion because the Ares I is from project Ares like Ares V and will be going with Ares V wherever it will go during the mission. For example to orbit the Moon and further exploration of Earth. The Ares I has the service module built in itself where the research is being done when in orbit or completing research on the journey. It will hold the results and stay in service when orbiting the Moon. The Ares I also has another abort system so astronauts should also be in the Ares I. Another reason the Ares I is important is because the Ares I secures the safety of the astronauts.
The Ares I stands 98 meters tall. The Ares I will help the Lunar Lander by extending it's service module. AS the Ares V orbits the Earth high the Ares I will orbit low on the Earth and there is a reason for that. NASA is trying to get all of the Earth during the orbit so project Ares will complete that part of the mission. The J-2X engine is extremely powerful so there will be no chance of the Ares I going off course. The Ares I is equipped with a 5 segment Solid Rocket Booster.
The Ares I serves as the long term launch capability for the U.S. and that proves that their can and will be no mistake in which the Ares I will be a part of. New liquid oxygen/liquid hydrogen is being tried on the Ares I and that is what the J-2X engine is being run on. The Ares I and the Ares V take heritage from the Apollo series which last did the Lunar phase of operations/missions. As soon as the launch is complete from the Florida Kennedy space center the upper stage and first stage of the Ares will separate. Further more the last objective on Earth for the Ares I will be for it's upper stage to orbit the Earth and from there the Orion shuttle will handle the rest.