The TVTropes Trope Finder is where you can come to ask questions like "Do we have this one?" and "What's the trope about...?" Trying to rediscover a long lost show or other medium but need a little help? Head to Media Finder and try your luck there. Want to propose a new trope? You should be over at the Trope Launch Pad.
Replay Value when a game is well suited to play beyond a single playthrough for any of many possible reasons.
Wide-Open Sandbox when a work just lets you loose in its world to explore. (Most of the core games in the Grand Theft Auto, Fallout, and The Legend of Zelda series are good examples)
Emergent Gameplay and Emergent Narrative are sister tropes for the widest-open sandboxes like Minecraft - the game provides a platform in which the player creates their own goals and storyline while interacting with the world.
Developer's Foresight and Combinatorial Explosion overlap when a work takes steps to avoid limiting a player's choices and/or reward tinkering and exploration. Noita is a good example, actively rewarding players for creatively abusing mechanics to game-breaking extremes. Scribblenauts is another, the developers taking hilariously extensive efforts to accommodate obscure words and bizarre player solutions.
Worldbuilding for lore that exists to give depth and breadth to a setting beyond the immediate story
Edited by Scorpion451

Of story content. Many side quests, for example, or many ways to upgrade your character.