By default, Inform reminds the player that they have the option of typing UNDO after a story-ending action. This is generally good practice, especially for the sake of novice players who might not be aware of this possibility otherwise, and might be frustrated by a loss they could easily step back from.
Cliff Edge is a room. "This narrow strip overlooks a gorge many hundreds of feet deep, at whose bottom is a river of molten lava. The walls of the gorge are lined with poison-tipped spikes. Furthermore, the birds that inhabit this valley spit balls of fire. Good thing you're safe up here."
The Table of Final Question Options determines what options are to be given to the player after the story ends. We can change what is mentioned there by altering the entries. (The example Jamaica 1688 explains this table in more detail, and demonstrates some other things that we might do with it.)