What does the action of playing a spell refer to?

Playing a spell specifically refers to the act of casting a spell or card from your hand, which involves paying its mana cost and following the necessary steps to have it enter the battlefield or resolve effects. When a player states they are "playing a spell," they mean they are taking the action to use that card, whether it’s a creature, instant, sorcery, etc., in accordance with the game's rules.

In contrast, drawing a card from the deck does not involve anything being cast or played; it’s simply adding a card to your hand. Revealing a card involves showing it to your opponent but does not equate to gameplay actions that change the state of the game or board. Similarly, activating a permanent's ability is a separate action that pertains to resolving a specific ability of a card already in play and does not involve playing a spell from the hand. Thus, the definition of playing a spell is tightly focused on the casting action and its associated processes.