As the Earth became more crowded and unable to support the life upon it, the humans living their started to attempt to move to new worlds.
To begin with Mars was attempted and then further afield along their own system.
Once the outer edge began to take form with moons being transformed into mining worlds and resource gathering and storing ports the rest of the universe was for the taking.
In the early days of colonization the trips could take several generations, but now that humans were cultivating space travel and attempting to get further and further into the great unknown the technology began to come along rapidly. Along with the introduction of different species and civilizations found among the stars. Though traveling between these stars could still take years, not the decades or even centuries it took in the beginning.
With the discovery of new civilizations came the sharing of new technologies, new ideas and of course some wars. Though wars have never been a massive thing within the claiming of land. Some colonist ships were never herd from again but the needs of the many out weighed the needs of the few.
As centuries have passed humans now spread out far and wide throughout the known galaxy.
Of course some of the earlier settlements have been affected by early colonisation techniques, the gravity on a world, length of day or general atmosphere has also cause some alterations and shifting of the human genome, which has caused some evolutionary changes to the ones living upon them over the centuries since they were first created, while other worlds have tried little experiments and created new ways to live which vary wildly from the initial human ideals.
These planet though seeming alien to some are still considered human colonies.
There are also the colonise that have been integrated into alien worlds and coexist with these different races. Though they do not all sit within the human trading agreements.
An then there are the Alien worlds, where no human would dare step foot..........