You can increase your stats by upgrading your units or equipping and upgrading gear. Here is a brief explanation of what each stat means.
HP: The amount of damage a ship can take before it is destroyed.
Attack: Increases the amount of damage a ship can deal. Most skills damage is calculated based on attack.
Defense: Lowers the incoming damage.
Hacking: Increases the chance for you to inflict debuffs.
Security: Lowers the chance of you being inflicted by debuffs.
Crit rate: The probability that crit damage will be applied to attack or repair.
Crit damage: Increased attack or repair output when compared to a regular attack or repair (needs crit rate to be applied).
Speed: How fast a ship is, expressed by how quickly it takes its turn each round. Units take their turns in order of highest speed to lowest.
For more information about hacking and security please see our article Here.