Titan was the second planetoid colonized by humans(not counting Earth's moon). It was first colonized in 2123. It When Titan was first settled, it wasn't really a "colony", it was more of a research base, and had a population of only 30. Now, in the year 2456, Titan has a population of over 34 million both in domed cities, and in mining outposts.
There are also stations near the methane lakes of Titan to collect the liquid methane and ship it off to remote colony worlds to generate electricity and to be used as fuel.
When exiting a building, a person must either be inside an atmospherically sealed vehicle, or have a sealed suit on, although being pressurized is not necessary due to the fact that Titan already has enough atmospheric pressure.
Enforcers attempted to take Titan in early 2454, but were repelled by GDA forces stationed on Mars who traveled quickly to titan and drove the Enforcers offworld.
There are roads on the surface of Titan to get from dome city to dome city, but only atmospherically sealed vehichles can travel on them.
There is a large orbital spaceport above Titan, both to export methane and ores, and to get people from large ships down to the moon's surface in small shuttles.