Jus ad Bello criteria is used before a war is started to determine whether entering that war is/was justifiable. Jus ad Bello generally breaks down into five categories: Just cause, proper authority, right intention, probable success, and proportionality.
Just cause is the core argument of Jus ad Bello and answers the question is going to war just. Just in the sense that the war is going to be fought to capture or to punish but rather as a last resort set against a grave threat or a great evil.
Proper authority is the idea that one waging the war is the head of state or duly appointed representative of the state.
Right Intention is linked to the previous criteria of Just Cause, that the war is being fought as a last resort to right a wrong and that it is not being fought for material gain or punishment of a people or state.
Probable Success is the idea that the war being under taken has a relatively high decree of success.
Finally, proportionality is the idea that the benefits must be the same or more than than the expected harms caused by waging war.
Jus in Bello is how combatants should act in a Just War. Three criteria are used: distinction, proportionality, and necessity.
Distinction is the idea that there is a discernible difference between combatants and non combatants and that acts of war should be directed towards combatants.
Proportionality in Just War is rooted in the idea of military gain vs incidental civilian injury. That is the gain from attacking a military target should never out weigh the amount of incidental civilian injury. If the gain from attack is little and the incidental injury is high than the attack should never be made. The weight and emphasis is on reducing incidental civilian injury.
Necessity is the idea that the minimum of force should be used and directed towards disabling the enemies military.
Jus post Bellum is criteria for determining justice after a war has finished. It is a reflection of Jus ad Bellum only applied to end of war issues. The only difference is that Jus post Bellum has the added criteria of discrimination. That is the losers burden, so to speak, should be focused on the those responsible for the prosecuting the war and not the population at large.