There are two settings in the Game Options menu, Land Expansion Limit and Naval Expansion Limit. The description tells me it limits the number of expansions the AI can have (in the name I guess?) but what exactly does this mean? What does the game consider an "expansion"?

I'm thinking it means it limits how far out from spawn the AI will choose to squat, but if I'm wrong please correct me. Google has been unhelpful in finding the answer.