Several things can happen when a pitcher tries to intentionally walk a batter.
1. The pitcher successfully tosses four pitches outside the strike zone, and all four are caught by the catcher.
2. The pitcher throws a ball nowhere near the catcher.
3. The pitcher throws the ball close enough to the plate that the batter smacks the ball into the outfield for a base hit.
This video shows what happens when 2 and 3 occur:
Why will you never see these again? Because the Real Smart People who run baseball decided a couple of years ago that intentionally walking a batter takes too long. So now a manager need only signal the home plate umpire, and the batter walks to first base, no pitch thrown. Gotta save that wasted three minutes so it can turn into five minutes for instant replay. Speeding up the game, ya know.