Obedience means that units are compelled to obey orders. Some may disobey if they believe the order goes against higher orders or their Ruler's interests Erf-b1-p005. Disobedience may cause the unit to disband.
Units are also required to follow any orders that require them to give sexual favors. The Earth idea of not taking advantage of a unit's obedience in this way is alien.summer-updates-044