Fantasy baseball is a game in which players win or lose based on the actual statistics compiled by major league baseball players. There are many fantasy sports, including football, basketball and hockey, but fantasy baseball was the first. It was created in 1979 and has transformed from a hobby practiced only by those with an extreme interest in baseball statistics to a multi-million dollar industry.
In a typical fantasy baseball league, anywhere from 10 to 16 people will "own" teams. There is usually a draft in which each owner picks real-life players to be on his or her team. Each owner must compile a roster that typically includes one player at each infield spot including catcher, three to five outfielders, a utility player - a position that can be filled with any batter, regardless of his actual position - and often other variations like "middle infielder" and "corner infielder." Each fantasy baseball team also has a pitching staff that can be filled with starters and relievers. The statistical output of these players determines the fate of the team.
The original style of fantasy baseball is called "Rotisserie" baseball. Each team competes in usually 10 statistical categories - runs, home runs, runs batted in (RBIs), stolen bases and batting average for hitters; wins, saves, strikeouts, earned run average (ERA) and walks/hits per inning pitched (WHIP) for pitchers - and possibly more or less depending on the rules of the league. The team in first place in a given category receives the most points, while the team in last place in that category receives the fewest. The points in each category are totaled, and the team with the most points wins.
The other type of fantasy baseball league is called a "head-to-head" league. This involves one team playing against another team for one week, with each team receiving a "win" or a "loss" in each category. The wins and losses are totaled for the entire season, and the team with the best winning percentage wins.
There are dozens of variations to the standard fantasy baseball rules. Different leagues have different types of drafts, different positions that must be filled, different categories that will be scored, and so on. Drafts can be held in person or on-line at any one of numerous fantasy baseball sites. There are also auction drafts, in which owners "bid" on players they want on their teams. There are even fantasy baseball leagues that use only National League players or only American League players. These are commonly referred to as NL-only and AL-only leagues.