In what year was the first MLB All-Star Game played?

What is a "pinch hitter"? What is the name of the spring training league held in Florida? What is the name of the spring training league held in Arizona? What is the highest level of minor league baseball? In what year was the first modern World Series played? Which team won the first modern World Series in 1903? In which city was the first All-Star Game played, at Comiskey Park? What happens on April 15 each year in MLB?