These are abilities you can use in combat, or which are automatically used.
1st level:
Armor Proficiency: You can wear all types of armour and use all types of shields.
Weapon Proficiency: All simple and martial weapons. No exotic weapons such as katanas, kukri or two-bladed swords. You can take the ‘Weapons: exotic’ feat if you really need it.
Divine Grace – Charisma modifier is added when making a saving throw.
Divine Health – Immunity to all forms of disease, a bit like a monk.
Lay on Hands – You can heal yourself once a day. How much you can heal increases with your level.
2nd level:
Aura of Courage – Immunity to mind spells such as fear
Smite Evil - Charisma modifier + Hit Die + Character Level are added to your damage.
3rd level:
Turn Undead – Banish or rebuke the undead, such as zombies, three times a day.
Remove Disease – You can cure your friends of disease once a day.
And that’s most of what’s needed when playing the righteous Paladin.