Shields are a secondary armor in Galaxy. Shields are designed to take damage before your hull starts to be damaged. Every ship in Galaxy is equipped with varying levels of Shield health. Damage to Shields is based on the type of Turrets and Spinals used when damage is being dealt. Planets and starbases also have Shield, excluding the NPC Abandoned U.N.E. Base at level 1. Shields will slowly regenerate over time.
Speed helps minimize physical damage to your ship. If you can outmaneuver the enemy ship with amazing dog-fighting skills, then you won't have to worry about your Shields or Hull too much. Cannons deal high damage to the Hull but deal low damage to Shields and travel slowly.
Shields are weak to specific Spinals. Phasers travel quickly and deal high damage to Shields but deal low damage to hull. Torpedoes do equal damage to Shields and Hull but require a longer time to reload and travel quite slowly. Speed always helps minimize damage to your Shields and ship overall. Keep in mind that the bigger your ship is, the more of a sitting duck you may be when your ship gets attacked by enemies.
"Laser" Turrets (more broadly called "Thermal" weaponry) also deal high damage to Shields, but low damage to Hull. As the size of the Turrets increases, so does the damage dealt to Shields, with Heavy Lasers dealing whopping blows with a base damage of over 100 health each.