Qualifying is closely related to the players, which was first extended by dota. Dota doesn't have the same grading mechanism as lol, but only has a list called ladder, and ranking means that players play games and rank their positions in the ladder according to the game results, so it is called ranking.
If the latter two are competitive sports. First of all, in the game, the points won in qualifying will be settled after a fixed period of time, which is called a season.
Regular season is the vocabulary of competitive sports, which refers to the general name of a game in which multiple teams fight in a season and score points according to the outcome. The winner gets one point, and the loser gets no points. This is the regular season.
Playoff refers to the current season, according to the points of each team in the regular season, the team with the highest points is selected to draw lots for the championship. And the competition in lol is the qualification for the world series.