The Thoron Distortion Field is a Set Bonus of the Aegis set (When you've equipped 2 pieces on the same ship). It Gives you a slight bonus to your defense whilst moving. Basically, when in combat, as long as your ship is moving, you get a slight defensive bonus.
The Reactive Shielding is a Set Bonus. (Again, Aegis) which activates when you have all pieces equipped. While your shields are on, your ship gets the passive ability "Reactive Shielding," which grants you a stacking defense bonus against a specific type of energy weapon. If you are fighting Klingons, or Romulans, you will get a stacking defense buff against Disruptor Damage. It stacks all the way to 10, but only affects your ship's hull (as far as I know) meaning as long as your shields are up, not much is happening.
The Aegis set is a craftable group of items, but if you don't have max crafting skill, it can be difficult to obtain. If this is the case, I recommend you ask someone to do it for you, or ask a member in your fleet (assuming you have one).