Complexes are basically a collection of prepared and secured modules that have been specialised. As per the rulebook, the quantity determines effectiveness of complexes.
Orbital docks move ships from orbit to the starport and vice versa.
Each orbital dock can support 25 hulls. Therefore a 100 hull ship will require 4 orbital docks to be active.
Domes, caves, command, mines, hiports, orbital docks, terraforming and bunkers do not count towards enclosed space requirement.