If it rains or gets too dark during a softball game, a few things can happen. The game will be over after five full innings, or 4.5 innings if the home team is ahead. If the game doesn't start up again, it's over and someone has won.
If the game didn't start because of rain or didn't go the full number of innings, it might be possible to make it up during the regular season. If the rain stops, the umpire can get the game going again. As long as the weather doesn't get in the way, the game can still happen.