Mlb
In short
Major League Baseball is the highest level of professional baseball in North America, consisting of 30 teams across the United States and Canada.
In plain words
It is the top baseball league in the world. Teams are split into two groups called the American League and the National League. They play many games every year to decide who wins the World Series.
A simple example
A team like the New York Yankees plays 162 regular games to try and qualify for the playoffs in October.
Why it matters
It is the premier competition for baseball talent globally. The league's championship, the World Series, is one of the most watched sporting events in North America.
Easy to mix up
Do not confuse it with Minor League Baseball, which is the developmental level below the majors.