If it is anything like EVE it just means that there are systems that work in real-time and operate even when you're offline.

For example, if you tell your colonists to built a factory... it may take 36 hours but you don't have to be online for them to work. Also, in EVE, your character's skill progression happens if you're online or not. Level 1 in a skill may take 2-3 minutes, and level 5 for some of the highest level skills could take weeks.