You have a deep-seated faith in and love for Gaia, God, or whatever higher power you believe in. You begin the game with one point of Faith (a Trait with a range of 1-10). This faith provides you with an inner strength and comfort that continues to support you when all else betrays you.
Your faith adds to your Willpower in times of dire need and gives +1 to the Dice Pool for each point in Faith. It doesn't aid rites, Gifts or any such abilities, however. The exact supernatural effects of Faith, if any, are completely up to the storyteller, although it will typically repel vampires and wraiths, if the player can succeed in a Faith roll against a difficulty of the opponent's Willpower. Faith has effects that differ from person to person and are almost never obvious - some of the most saintly people have never performed a miracle greater than managing to ease the suffering of an injured soul.
An additional benifit of True Faith is innate protection from the power of mages - each point of Faith acts as a die of countermagick against the Effects of the Namers.
True Faith is a rare attribute in this day and age. Only mortals may start the game with more than one Faith point. Additional points are awarded only at the Storyteller's discretion, based on appropriate behaviour and deeds.
(For the most complete look on True Faith, see The Inquistion, pp. 63-71. Although many of the catechisms of the Church are inappropriate for Gaian faiths, that book nonetheless treats Faith in the detail it deserves.)