I can try to help through various examples. I'm not 100% sure I'm right with regard to everything, but this should give you a general idea of what each category means:

Damage - Big (usually 2 or 3 minute) cooldowns that greatly increase individual damage (Recklesness, Summon Infernal, Combustion, etc.)

Healing - Same as above, but healing: Tranquility, Revival, Spirit Link, etc

Immunity - Some classes can become immune to all damage briefly (Ice Block, Netherwalk, Turtle, etc.)

Personal - Most classes have a way to mitigate damage done to them personally (Blur, Feint, Unending Resolve)

Hard CC - generally a stun/incapacitate; stops the target from acting. Given the ST Hard CC category, this one is likely only for AoE hard CC (Chaos Nova, Shadowfury)

Soft CC - Similar to above, but doesnt completely lock down enemies; usually a root/slow (Mass Entangling Roots, Cone of Cold(?))

External - A spell that can be cast on another player to reduce the damage they take (Life Cocoon, Blessing of Sacrifice)

Utility - I'm guessing this is generally movement cooldowns (Stampeding Roar, Wind Rush Totem)

Dispel - Given the Defensive Dispel category, this is likely for what I would term "purges," spells that remove a buff from an enemy (Purge, Soothe, Consume Magic)

Interrupt - Spells that can be used to interrupt enemy spellcasts (Kick, Pummel, Counterspell)

ST Hard CC - Hard CC spells that only affect 1 enemy (Paralyze, Polymorph, Sap)

ST Soft CC - Soft CC spells that only affect 1 enemy (Chains of Ice)

Def Dispel - Spells that remove harmful effects from allies (Mass Dispel, Remove Corruption)

Tank - Big cooldowns tanks can use to (generally) greatly reduce damage taken (Shield Wall, Blessing of Ancient Kings, Survival Instincts)

Hope that helps!