In this section i will go through the most important skills of paladin. There are a lot more of them but they are so situational that you can literally tank with these skills till some point.
Cannon regeneration
As paladins some of your skills use 2 different types of cannons. These skills are in the build are giving more of them after use.

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Seal of Righteousness/Retribution/Vengeance/Pledge of Purity :
All of these skills have only 1 job and its to give cannons. Seal of Righteousness gives Cannon of Purity, Retribution gives Cannon of Light and Vengeance (racial skill) gives 1 each of the cannons. Retribution doesnt have cooldown, but Seal has couple second cooldown and Vengance has 1min cooldown as racial skill. Pledge of Purity is used while in combat to give Cannon of Purity every couple of seconds while the buff is on.
Barrier Skills
Like said earlier, Paladins can manipulate their the dmg they recieve into their barriers.

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Defensive Screen/Martyr's Shield/Overcome :
These skills are used to lower the dmg paladin takes through the barriers. Defensive Screen removes the highest hit on the barriers with bit of a cooldown. Martyr's Shield heals you 9% from the dmg you got in the barriers and moves the dmg into 1 barrier so you get 3 empty barriers after using this. Overcome reduces the highest dmg in your barriers by 50% and inflicts the rest straight into you.
Aggro Skills
As a tank, we obviously have skills that make a lot more aggro when we use them.

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Challenge/Massive Challenge :
These skills are both doing the same thing, only difference is that Massive Challenge taunts all targets 20 yards around you, Challenge only taunts one target. Both force target(s) to attack you for 5 seconds or till you lose 20% of your max hp.
Dmg Reduction/Shielding
These skills are used to decrease the dmg you are taking or just purely shielding you.

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Holy Ground/Rage of Light/Shield Slam/Strike of Justice/Veil of Light :
Holy Ground and Rage of Light are similar, both make "circle" around you while inflicting small amount of dmg to enemies around. Holy Ground drops to the ground and Rage of Light moves with you. Both of these decrease the dmg you are taking while they are on. Shield Slam stuns the target and increases aggro, but the main point is to use this while standing on your Holy Ground, then this skill gives you are a massive shield. Strike of Justice is really nice gap closer and same time it gives 50% reduced dmg buff. Veil of Light just gives you and your party members really decent sized shield.
Optional

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Pledge of Vengeance/Blood Aegis (reinc skill)
Pledge of Vengance is buff applied to party member to decrease dmg that they are taking for 25% (really good on healer/support) and if that target dies, you will be healer by 50% of your max hp. i recommend to use Blood Aegis as reinc skill since it reduces dmg that you take by 20% for 10 seconds.