T-Ball, or Teeball, is a sport based on baseball and is intended as an introduction for children to develop baseball skills and have fun. The origins of T-ball are not certain, but it is believed to date back to the 1940s or 50s.
In T-Ball, the pitcher is usually used for defensive purposes only. The ball is placed on an adjustable tee atop the home plate at a suitable height for the batter to strike. Most of the other rules are similar or identical to those of baseball, though the game is played on a smaller field.
Often, the score is not kept and rules are designed to maximize participation: an inning is completed once each child has had a turn at bat and all extra players of the defensive team play in the outfield every inning. To encourage the defensive team to try to make plays, there are typically no extra bases on overthrows and runners may not advance after the ball is in possession of an infielder.
For more information, click here: http://www.teeballusa.org/