OP lacks info on races.
Argons: Humanity, separated from the Sol system several hundred years prior to X3: Terran Conflict. Their ships are average in every way, capable of doing any task but not being particularly great at it. Capital ships are huge monolithic bricks, while their small fighters resemble jet fighters in space. Allied with the Boron, and dislike the Paranid
Boron: Space hippy squids, pretty much. Their fighters are fast and poorly armed but have special weapons, and their capital ships are very powerful but usually have a big achilles heel. All their ships resemble aquatic life, and have iridescent hulls. Allied with the Argon, and dislike the Split
Teladi: Hyper-capitalistic amphibians. Their craft are slow as stuff and look like they were cobbled together from junk, but they have a forgetton of shields and huge cargo bays. Neutral to all races, including Pirates.
Paranid: Theocracy of beetle-like aliens. Their ships are some of the most powerful of all races, but have pathetic cargo bays and are usually very expensive. Ships look like something out of Star Trek. Allied with the Split, dislike the Argon.
Split: Humanoids obsessed with fighting (think Klingons). Their ships are very fast and powerful, but have poor shield strength. Ships are very angular and blade-like. Allied with the Paranid, and dislike the Boron.
Terrans: The human government residing in the Sol System, separated for hundreds of years from the Argon. Their ships are far superior in every way to the other races, but lack variety in weapons and are extremely expensive. All their ships are blindingly white, with their fighters looking like a futuristic jet-fighter and their capital ships looking like uh, LEGOs.
ATF: Not a race, but the military of the Terran government, specifically for dealing with the Xenon. Their ships are a mash of odd angles, and look somewhat like the Forerunner technology of Halo. They can easily overpower any single ship in the game.
Goner: Not a race, but a faction of Argon citizens that believed in the existance of Earth. Their ships are unarmed and slow, but their capital ships are massive and can dock other capital ships to them.
Pirates: Not a race, but a faction comprised of every species in the X-universe. Their ships are old and outdated, with flame paintjobs. Their ships are usually stolen Argon, Teladi, and Split ships, with the occassional unique pirate-built ship. Attacks all races, except Teladi.
Xenon: Terraformer drones sent out by the Terrans hundreds of years ago, software glitch caused them to start "terraforming"
everything, including stations and ships. Their ships have no generic stats, with each class having wildly different stats. Ships resemble partially finished buildings with their innards exposed. Attacks all races.
Kha'ak: Hive mind bugs. Their light fighters have paper armor and weak weaponry, but their capital ships are extremely powerful. Fighters look like flying pyramids, while the capital ships look like hives. Their fighter craft also tends to come into battle linked up, and then split when engaged. Attacks all races.
Yaki: Pirate faction. Their ships are usually customized Paranid ships, mixed with unique Yaki capital ships. Attacks all races, including Pirates.
?
The human population in the Sol system are called Terrans, while the rest of the human species are members of the Argon, Goner, or Aldrin. The Terrans have been isolated from the rest of the races but were reunited in X3: Reunion. Their technology is far superior to the rest of the races, and they dislike all aliens.
