Of what special assistance are the swords Orcrist and Glamdring?

"This sword's name was Glamdring the Foe-hammer, if you remember. The goblins just called it Beater, and hated it worse than Biter if possible. Orcrist, too, had been saved; for Gandalf had brought it along as well, snatching it from one of the terrified guards. Gandalf thought of most things; and though he could not do everything, he could do a great deal for friends in a tight comer."

The swords were beautiful and are of special assistance because they would glow blue in the presence of Orcs.