T.2.1- The stack is the core of the timing rules for Magic. It is called a stack because each announced spell or ability is placed on top of the pile, forming a stack. When they resolve or are countered, they are removed from the stack. So the stack grows and shrinks over time. [CompRules 1999/04/23]
T.2.2- The timing for the stack looks like this: [CompRules 1999/04/23] 1. The active player may announce a spell or ability legal at this time: a. The active player may announce a spell or ability (see Rule T.4) and add it to the stack. b. Goto 1 if something is announced in 'a'. c. If the active player chose not to announce something, they "yield priority". If the active player does this without announcing something first, and this is done after just the other player has yielded priority, goto step 3. 2. If the active player yields priority, the other player may announce a spell or ability legal at this time: a. The other player may announce a spell or ability (see Rule T.4) and add it to the stack. Not playing something is called "yielding priority". b. Goto 2 if something is announced in 'a'. c. If the player yields priority but did announce something before doing so, goto 1. If nothing was announced by the player, goto step 3. 3. Once both players yield priority (active player then other player, or the other way around), if there are any spells or abilities on the stack, resolve (see Rule T.6) the top item on the stack, then go to step 1. If there are no spells or abilities on the stack, end the current phase or step.
T.2.3- The active player is the player whose turn it is. [CompRules 1999/04/23]
T.2.4- A spell or ability can be countered (see Rule G.7). If this happens, it is removed from the stack and does not resolve. Thus, all of its costs were paid but none of its effects occur. [CompRules 1999/04/23]
T.2.Ruling.1- Adding something to a stack with spells or abilities on it is called "responding" to a spell or ability. [CompRules 1999/04/23]
T.2.Ruling.2- The stack resolves in last-to-first order. This means the last played spell or ability actually resolves (see Rule T.6) first. Then the next to last, and so on. This can result in things being different than you expect sometimes, but it works to allow the responding player to get an advantage. [D'Angelo 1999/05/01]
T.2.Ruling.3- A spell or ability may remain on the stack for quite a while if players continue responding to it. There is no limit to how many spells or abilities can be announced and resolved before letting a spell or ability on the stack resolve. [D'Angelo 1999/05/01]
T.2.Ruling.4- Players may also take actions that do not use the stack any time they have priority. Those actions resolve immediately and give that same player back priority. [DeLaney 2003/06/15]
Note- Mana abilities do not go on the stack, see Rule A.6.2.
Note- Playing land cards do not go on the stack, see Rule K.15.2.
Note- Also see Stack Zone, Rule Z.9.