The stats of a unit refers to a unit's attack, health, range, etc. There are 7 different stats: attack, defence, movement, range, health, cost, and skills. The stats of a unit depend on what kind of unit it is. For example, most melee units will have higher health and defence than most ranged units.
The Warrior model, with his stats on the right.
Attack
Attack refers to how much damage a unit does. A unit's attack damage decreases as the unit gets damaged. For example, a warrior with 10 health and 2 attack will deal 5 damage to another warrior, but a warrior with 3 health will only deal 2 damage to another warrior. For more in-depth information about attacking, visit the Combat page.
Defence
Defence refers to how much damage a unit will do after being attacked. Defence damage also decreases as the unit loses health. A warrior with 2 defence and 10 health will deal 5 damage to another warrior if attacked, but a warrior with 3 health will only deal 2 damage if attacked by another warrior. Defence also determines how much damage a unit takes. A defender, which has 3 defence, will take usually less damage than a warrior, which has 2 defence. Cities and some terrain types will give certain defence (as in damage taken) bonuses after researching the right technology or choosing the right upgrade.
Movement
Movement determines how far a unit can move per turn. A knight, with movement 3, can move 3 field tiles per turn. However, certain tiles require certain movement points. For example, forests require 2 movement points, so a knight can only move 1 forest and 1 field per turn. You can decrease the movement cost of any terrain by putting a road on it.
Range
Range determines how far a unit can attack. An archer, which has range 2, can attack any unit that is 2 tiles away. Range is calculated starting from the tile in front of the unit to the tile that the enemy unit is on.
Health
Health refers to the amount of damage a unit can take. As stated above, it also determines the attack and defence(as in defensive damage) of a unit. Units can replenish health by using the recover ability, which will replenish 4 health if the unit is in your territory or 2 health if the unit is not in your territory, or by using the Heal Others ability of the Mind Bender.
Cost
Cost refers to the amount of stars needed to train a unit. Generally, more powerful troops require more stars to train.
Skills
Skills refer to the skills of a unit. Units can have various skills, such as ability to attack after moving (Dash) or the ability to move after attacking (Escape). For a more detailed explanation, visit the Unit Skills page.