From IFWiki

A successful conclusion to an IF work, involving the completion of all or most of the game's important goals. In a work with multiple endings, a win is usually a favorable conclusion to the narrative. Some experimental IF (for example, Adam Cadre's 9:05) is designed so that the ending that is most positive for the PC is anti-climatic for the player. (See also: multiple endings, optimal ending, losing and death.)

Reaching a final reply that indicates the achievement of the IF game's goals.