This addon helps you make sure you have all the buffs you should have, that your target and focus target have the debuffs they should have, and that you're using your spell and item cooldowns as often as possible. It does this by letting you set up monitors for the buffs, debuffs, spells/skills and items you're interested in. The monitors appear visually as standard action buttons on the screen.
When everything is ok (you have the monitored buff, your target has the debuff, the cooldown is running, ..) the corresponding button is faded out. When something is missing or the cooldown is up the button becomes fully opaque, signaling that something needs to be done. Buttons that represent skills/spells/items you have can be clicked to trigger the appropriate action.
Use /polmonitor to configure.