Stats are a ship's preset attributes that give the player an indication of how well a particular class of ship would fare against itself or against another, as well as how many of a ship would be needed to completely destroy a particular fleet. Damage, Shield, and Armor can be increased (by percentage) by way of Flagship Modules and research. A ship's stat list can be viewed by tapping/clicking on the ship model in the Shipyard.
Damage[]
Damage is how strong of an attack a ship puts out each turn. A ship with Damage higher than an opposing ship's Shield/Armor will beat that ship. If the ship's Damage is too low, more and more ships can be added to increase the effect, as Damage stacks.
Shield[]
Shield is the first component of a ship's durability.
Armor[]
Armor is the second component of ship's durability.
Targets[]
Targets are the number of ships a particular class can take out at one time, provided the Damage is high enough and the opposing ships' Shield/Armor are low enough.
Cargo[]
Despite having specific ships to carry cargo, all ships have their own cargo space. Many of the attack ship classes have incredibly low cargo space, however, which is why the cargo ship classes are used for such a purpose.