This is display in the tooltip DPS for certain abilities as DPS divided with weapon speed

This option means the manually set (custom stats, like spelldamage etc) are added to your current stats.

This is for abilities that have a chain effect, i.e. chain lightning, chain heal

This displayed in tooltips of abilities with additional effects, the avg stands for the avg damage/heal increase and the proc is the damage/heal when the ability triggers. Example: Frostbrand Avg/Proc: 100/300