Whenever you
castTo cast a spell is to take it from the zone it’s in (usually the hand), put it on the stack, and pay its costs, so that it will eventually resolve and have its effect. A player may cast a spell if they have priority. See rule 601, “Casting Spells.”
To cast a card is to cast it as a spell. (CR 701.5) a signed spell or
playTo play a land means to put it onto the battlefield from the zone it’s in (usually the hand). A player may play a land if they have priority, it’s the main phase of their turn, the stack is empty, and they haven’t played a land this turn. Playing a land is a special action (see rule 116), so it doesn’t use the stack; it simply happens. Putting a land onto the battlefield as the result of a spell or ability isn’t the same as playing a land. See rule 305, “Lands.”
To play a card means to play that card as a land or to cast that card as a spell, whichever is appropriate.
Some effects instruct a player to “play” with a certain aspect of the game changed, such as “Play with the top card of your library revealed.” “Play” in this sense means to play the Magic game.
Previously, the action of casting a spell, or casting a card as a spell, was referred to on cards as “playing” that spell or that card. Cards that were printed with that text have received errata in the Oracle card reference so they now refer to “casting” that spell or that card.
Previously, the action of using an activated ability was referred to on cards as “playing” that ability. Cards that were printed with that text have received errata in the Oracle card reference so they now refer to “activating” that ability. (CR 701.18) a signed land, copy it. (A signed card is a card signed by its artist, designer, or someone else it's strongly associated with.)
DiscardTo discard a card, move it from its owner’s hand to that player’s graveyard.
By default, effects that cause a player to discard a card allow the affected player to choose which card to discard. Some effects, however, require a random discard or allow another player to choose which card is discarded.
If a card is discarded, but an effect causes it to be put into a hidden zone instead of into its owner’s graveyard without being revealed, all values of that card’s characteristics are considered to be undefined. If a card is discarded this way to pay a cost that specifies a characteristic about the discarded card, that cost payment is illegal; the game returns to the moment before the cost was paid (see rule 733, “Handling Illegal Actions”). (CR 701.9) a signed card:
DestroyThe only ways a permanent can be destroyed are as a result of an effect that uses the word “destroy” or as a result of the state-based actions that check for lethal damage (see rule 704.5g) or damage from a source with deathtouch (see rule 704.5h). If a permanent is put into its owner’s graveyard for any other reason, it hasn’t been “destroyed.”
A regeneration effect replaces a destruction event. See rule 701.19, “Regenerate.” (CR 701.8) target creature with a name that has a five or fewer letter length difference from the person who signed the discarded card.