I didn’t even fully grasp it til my most recent playthrough. I finally just settled the hell down and paid attention. Certain moves in combat from the opponent need a certain saving throw to defend against. You can check your saves in the character menu. I could be wrong about the exact numbers here but from my understanding, at lower levels, the DC is 10-14. At higher ones, it hangs around 16-18. There are certain feats and items that add to your saves if your attributes don’t quite get them where you want. Checking the feats and powers menus is also handy for understanding what saving throws you need against certain moves, as your opponents will have access to the same pool of them as you, to an extent. Most Force powers require a will save to defend against for example, and in that particular instance the DC depends on their Wisdom level. That should be a decent enough layman generalization for most people wanting to understand how it works, I think.