On a large ship there was usually more than one Mate aboard (hence the title "First Mate").
Mates served as apprentice to the Ship's Master, Boatswain, Carpenter & Gunner and took care of the fitting out of the vessel, and examined whether it was sufficiently provided with ropes, pulleys, sails, and all the other rigging that was necessary for the voyage.
The Mate also took care of hoisting the anchor, and during a voyage he checked the tackle once a day. If he observed anything amiss, he would report it to the ship's Master. Arriving at a port, the mate caused the cables and anchors to be repaired, and took care of the management of the sails, yards and mooring of the ship.