Not much is explained about the Space Jockeys. Our first and only time that we saw one in a movie is in Alien, the dead one that was chestbursted. Their connections to the Xenomorph although isn't clear, it has been established that they have to do something with the Xenos being there. Wether they created the Xenomorph and was killed by them, or that they simply wanted to use them as bio weapons and ended with the same result. Unlike with the Xenos, their connection with the Predators are unknown. Because of the comics and AVP, some have speculated that they were "ordered" by the Predators to make and breed the Xenos as prey and the Xenos escape. Some say that the Preds threatened their existence, so they tried to use the Xenos as weapons against the Preds.
Since not much information is given on their race, most is up to speculation and theories. Which one is real? It's all up to you.
"There are five possible operations for any army. If you can fight, fight; if you cannot fight, defend; if you cannot defend, flee; if you cannot flee, surrender; if you cannot surrender, die."