What does it mean that I've "reached the end of the world"?

I received this message:

You have reached the end of the world

What does this mean? I've gotten this message once or twice. While I can still see inside of the map, there seems to be some empty area left? Is it possible to go there or this is the limit of the accessible area in the game?

2 Answers

Even though the map shows more you have reached the edge of the accessible world.

If you continue to move on far past this point the map will be shown automatically and you can fast travel.

This is really the end. You can't go further even if you can see something out there. It's like an invisible borderline on the floor.