In basketball, the "Shot Clock Era" refers to the time after the introduction of the shot clock to the game. The shot clock was innovated by the National Basketball Association in the 1954-1955 season, and was eventually adopted by other professional leagues, as well as by college FIBA basketball.
The introduction of the shot clock quickly revolutionized the game, both in terms of style of play and popularity. Basketball teams could no longer freeze the game by holding on to the ball while ahead, and this led to a more up-tempo game, with higher scores. And this, in turn, led to a more popular game.
Because of the changes it brought about in basketball, the introduction of the shot clock tended to separate the sport's history into a before and after. Especially in the field of basketball records, the term "Shot Clock Era" is used as a qualifier. Because the style of play was so different afterwards, the records of players and teams before the introduction of the shot clock are usually not directly compared to records after the introduction. For example, before the introduction of the shot clock, the record low points for a team in a game was 18. In the sixty years since its introduction, the lowest amount of points was 49. It was a radical innovation in the sport that clearly separates what came before from what came after.
It is also possible to talk about other eras in the history of basketball, because the sport's rules have changed steadily over the years. For example, there is probably a "Three Point Era", but none of these changes have led to the sudden and drastic changes that the introduction of the shot clock did.