Introduced in the Onslaught block, Cycling has been reprinted a number of times as it is a very popular mechanic.

702.26. Cycling

• 702.26a. Cycling is an activated ability that functions only while the card with cycling is in a player's hand. "Cycling [cost]" means "[Cost], Discard this card: Draw a card."
• 702.26b. Although the cycling ability is playable only if the card is in a player's hand, it continues to exist while the object is in play and in all other zones. Therefore objects with cycling will be affected by effects that depend on objects having one or more activated abilities.
• 702.26c. Some cards with cycling have abilities that trigger when they're cycled. "When you cycle [this card]" means "When you discard [this card] to pay a cycling cost." These abilities trigger from whatever zone the card winds up in after it's cycled.
• 702.26d. Typecycling is a variant of the cycling ability. "[Type]cycling [cost]" means "[Cost], Discard this card: Search your library for a [type] card, reveal it, and put it into your hand. Then shuffle your library." This type is usually a subtype (as in "mountaincycling") but can be any card type, subtype, supertype, or combination thereof (as in "basic landcycling").
• 702.26e. Any cards that trigger when a player cycles a card will trigger when a card is discarded to pay a typecycling cost. Any effect that stops players from cycling cards will stop players from playing cards' typecycling abilities.

702.26. Cycling

• 702.26a. - You cycle a card as an activated ability while the card is in your hand. The game doesn't care if the cycled card makes it to the graveyard or not.
• 702.26b. - Even though you can only cycle a card from your hand, the card continues to have cycling.
• 702.26c. - If the card does something after being cycled, it happens whether the card makes it to the graveyard or not.
• 702.26d. - There's a subtype of cycling called Typecycling. Instead of just drawing a card, you search your library for the named type of card.
• 702.26e. - Abilities that stop you from cycling cards also stop you for typecycling.