Remove Curse is a core mage ability learned at level 29. It removes all curse-type debuffs from a friendly target player.
Druids have also a spell named Remove Curse, both spells are capable of removing the same curses.
In PvP, removing the curses from allies under attack from a warlock is much appreciated and can turn the battle against the opposing warlock.
The following macro will cast Remove Curse on the target underneath your mouse pointer, without losing your current target. This is handy if you have a group or raid party frame that prominently displays curses that you can remove. Simply hover the mouse over the target and tap this macro.