In a world, I type:

1. /title @p title Something (appears Something as title)
2. /title @p times 10 100000000 10 (makes the title wait for a long time on screen)

Then I "save and quit" (before it goes away) and go to another world. In that world the same title appears (without typing anything or activating any previous command).

This affects gameplay when a client plays in a map (and does the command), and then goes to another that doesn't allow commands (cheats). Then the player would have to play the entire map with the title on the screen until it fades away or go to a map with commands enabled and clear the title (or reset).