The Warrior ability grants a bonus of 10 points to the Strength and Enduranceattributes. These bonuses are permanent, however once the respective attributes reach 100 this sign has essentially no effect. Perfect fit for fighters; attribute bonuses are always a safe bet.
(Summary and picture from Official Elder Scrolls Site)
Your starting health is twice that of your starting Endurance. Your health raises one tenth of your Endurance every level. Increasing strength and Endurance helps boost starting fatigue.
For those reasons this birthsign is a safe choice for close range fighters that want maximum health and melee damage.