In the current NBA format, the NBA is structured into two conferences — the Eastern Conference (e.g. Boston Celtics, Philadelphia 76ers, New York Knicks, etc.) and the Western Conference (e.g. Los Angeles Lakers, Golden State Warriors, San Antonio Spurs, etc.) — with 15 teams in each, primarily organized based on geographic location. In the regular season, teams play 82 games where they face teams from the other conference two times and teams from the same conference three or four times. At the end of the season, teams are seeded based on wins in relation to teams within their respective conference. The top teams then proceed to the play-offs.
In the current playoff system, teams are seeded within their respective conferences based on regular season performance with the top 6 in each conference qualifying for the playoffs and the 7th-10th teams in each conference entering the Play-In Tournament where teams compete in a single elimination format to determine the lowest playoff seeds at each side of the bracket. In the current format, teams from the East and West can only face each other in the NBA Finals of the play-offs.
In a single-league playoff system, the teams are seeded regardless of conference affiliation. Under this model, teams are seeded 1 through 16 based on the total number of wins (e.g., 1 vs. 16, 2 vs. 15, etc.) with the top 12 teams across the league qualifying for the playoffs, and the 13th-20th teams competing in the Play-In tournament. This format abandons the East West conference structure in the play-offs.