The Holy Warrior is a class that replaces the Paladin in the PHB. Essentially it is a Paladin but with customized powers based on the church the Holy Warrior serves. Holy warriors of the Great Church are exactly like Paladins in the PHB.  There is too much information on all the powers and abilities of all of the Holy Warriors for me to want to present it all here.  If one of them catches your interest let me know and I'll send you the complete information for a specific Holy Warrior.

Holy Warrior Game Rule Information

Alignment- Always good and the same lawful or chaotic leaning as their patron deity.
Hit Die- d10
Class Skills- Concentration (Con), Craft (Int), Handle Animal (Cha), Knowledge(religion) (Int), Profession (Wis), and Ride (Dex)
    -Every order of Holy Warriors receive 2-3 additional class skills see table 3 below.

Spells- A Holy Warriors spell list is dependant on their patron church. Their selection of spells will be limited in a similar way as the sorcerer, only more generous.  A table of Holy Warrior spells known per level can be found here.

Gift of God- Is a special ability, like the paladins ability to remove disease, that is dependant on the Holy Warrior's patron church. See table 2 below.

Turn Undead- Holy Warriors turn undead as Paladins of the same level.

Special Mount/Companion- Holy Warriors receive a special mount or animal companion.  The type of companion is dependant on the patron church. See table 2 below.

Domain Abilities-When creating a Holy Warrior choose two Holy Warrior domains from the available domains in the Holy Warriors patron church.  Each of these domains gives the Holy Warrior two special abilities at first level and one special ability at second level.  The descriptions of these powers can be found in the Book of the Righteous and the PHB. The Holy Warrior domains for each church can be found in the churches section.