Why was Pickett's Charge important?

During the American Civil War, the 1863 Battle of Gettysburg featured on its third and final day the famous "Pickett's Charge" by Confederates that tried but failed to break the Union center. It is important in respect to the battle itself because its failure ensured a Union victory: given the casualties suffered during the unsuccessful attack, the South could no longer manage successful offensive action, and one day later it began to retreat southwards once again.