Give me an overview of how promotion and relegation works in the English Premier League

Competition
There are 20 clubs in the Premier League. During the course of a season (from August to May) each club plays the others twice (a double round-robin system), once at their home stadium and once at that of their opponents, for 38 games. Teams receive three points for a win and one point for a draw. No points are awarded for a loss. Teams are ranked by total points, then goal difference, and then goals scored. If still equal, teams are deemed to occupy the same position. If there is a tie for the championship, for relegation, or for qualification to other competitions, the head-to-head record between the tied teams is taken into consideration (points scored in the matches between the teams, followed by away goals in those matches.) If two teams are still tied, a play-off match at a neutral venue decides rank.[83]

Promotion and relegation
A system of promotion and relegation exists between the Premier League and the EFL Championship. The three lowest placed teams in the Premier League are relegated to the Championship, and the top two teams from the Championship promoted to the Premier League,[84] with an additional team promoted after a series of play-offs involving the third, fourth, fifth and sixth placed clubs.[85] The number of clubs was reduced from 22 to 20 in 1995, when four teams were relegated from the league and only two teams promoted.[86][87] The top flight had only been expanded to 22 teams at the start of the 1991–92 season – the year prior to the formation of the Premier League.[87]

On 8 June 2006, FIFA requested that all major European leagues, including Italy's Serie A and Spain's La Liga, be reduced to 18 teams by the start of the 2007–08 season. The Premier League responded by announcing their intention to resist such a reduction.[88] Ultimately, the 2007–08 season kicked off again with 20 teams.[89]

The bottom 3 teams in the Premier League are relegated to the EFL Championship. The top 2 teams and the winner of a tournament between the 3rd through 6th ranked teams in the EFL Championship are promoted to the Premiere League.