The Vulcans are a race very similar to the human race. One major differance is their emotional state. Vulcans get emotions they just choose to supress them. This puts them in a state of logic, where everything has to be logical to be worth doing. In ancient times on their homeworld, also named Vulcan, all the people had and used emotions. Their emotions were so strong that it corrupted their world. Then a Vulcan guy came along and brought order to the society. The Vulcans history in Star Trek started when Zephram Chocrane (the man who first invented warp drive for humans) went into warp for the first time on his ship, the Pheonix. After he landed back on Earth, the Vulcans detected his warp signature, and altered their science mission to investigate. Soon after first contact was made on earth between the Vulcans and the humans.
Now, in the 24th century, the Vulcans play a big part in Starfleet and the Federation. Any Vulcans who wished to explore in space wsould most likely join Starfleet, because the Vulcan facilities aren't as great. However, the Vulcan science facilities are said to be top notch.