Damage types & their effects..?

I've noticed that there are various types of damage: earth, lightning, cold, fire, dark, chaos, holy... but whats the difference between them?

I've noticed that lightning is often paired with armor penetration, cold damage to slowing... but what about the others? Whats different about dark damage to chaos damage? Are they more effective vs certain types of foes?

Is there some type of guide to the (dis)advantages of the different damage types?

I'd like to know this too actually, I recently purchased a sword that does 15-22 earth damage and I'd like to know what exactly that means for me!

Certain enemies and players have resistances to certain types of damage. Like a Ranger has resistance to elemental damage (lightning, fire, cold, etc) build in their armor, while a warrior has build in resistance to purely physical damage. So an earth sword would do more damage to a warrior than a regular physical attack, while the earth sword would probably do less damage to a ranger.

Also for example the Ice Fiend things that can be found in the mountains die REALLY quick from fire based attacks.

What about chaos, dark, etc? Are certain enemies more susceptable to these types? Do they have any other effects, like ignoring armor or something?