Every starship has shields, which are energy fields that serve as protective barriers. For non-combat ships, shields simply serve to prevent small asteroids from damaging the ship; for larger combat ships, they provide the initial defense against attacks from other ships. Shields are different from armor in that they recharge (albeit slowly) between attacks.
The most potent weapons against shields are EMP Torpedoes and Ionic Particle Cannons, although Compound Blasters and most Polaris weaponry are also effective. Missile weaponry, Fusion Pulse weapons, and Hail Chainguns are more effective against armor than shields.
There are a number of outfits that can increase your shield capacity:
Most ships do not have a very significant shield recharge rate, but these outfits can make shields recharge faster: