The Relocation is the mass exodus from Old Earth by the majority of humanity. Old Earth had reached a so-called tipping point in the sustainability of life and to preserve it, humans took themselves and all the other walks of life they could to Luna and Mars.
When it became a mandate to leave the planet, there was some resistance from lesser intelligible groups of people, and those who felt like they shouldn't leave for miscellaneous reasons. Most of these groups were uprooted and shipped off planet, but some became rebellious and either eluded capture or fought to stay.
Needless to say, those that actually fought, lost, and were either captured or killed. Those that eluded capture wait for the day they are eventually captured by Sybil Earth Mining's security forces and sent off-world.