Question: The 76ers–Celtics rivalry is a National Basketball Association (NBA) rivalry between the Philadelphia 76ers and the Boston Celtics, the two teams have the most meetings in which playoffs are a best-of-seven elimination tournament among 16 teams in the Eastern Conference and Western Conference (called divisions, pre-1970), ultimately deciding the league's season champion in the NBA Finals?
Context: The 1979–1980 Philadelphia 76ers season was the 76ers 31st season in the National Basketball Association (NBA) and 17th season in Philadelphia.  They finished with a record of 59–23, their best since the 1967–68 season.  The team had acquired guard Lionel Hollins from the Portland Trail Blazers after their effort to obtain Pete Maravich failed as he signed with the Boston Celtics.  In the playoffs, they won the 1980 Eastern Conference Championship over the Boston Celtics 4–1.  In the 1980 NBA Finals they would lose to the Los Angeles Lakers 4–2.  The series was memorable for Julius Erving's baseline move in Game 4, and Magic Johnson's 42-point effort in Game 6 starting the game at center in place of an injured Kareem Abdul-Jabbar. The 1965 NBA World Championship Series was the championship round of the 1965 NBA Playoffs, which concluded the National Basketball Association 1964–65 season.  The best-of-seven series was played between the Western Conference champion Los Angeles Lakers and the Eastern Conference champion Boston Celtics.  The Celtics made their ninth-straight trip to the championship finals after beating the Philadelphia 76ers in a highly contested Eastern Division Finals that ended on John Havlicek's steal of the ball.  The Lakers made it to their third Finals in four seasons after beating Baltimore in six games, though it came at a cost as Elgin Baylor suffered a knee injury that would sideline him for the rest of the playoffs.  The Celtics won the series over the Lakers, 4–1. The 1967 NBA World Championship Series was the championship series of the 1966–67 National Basketball Association (NBA) season, and was the conclusion of the 1967 NBA Playoffs.  The best-of-seven series was played between the Western Conference champion San Francisco Warriors and the Eastern Conference champion Philadelphia 76ers.  This was the first championship series in 11 years without the Boston Celtics, who were defeated in the Division Finals by Philadelphia. The 76ers–Celtics rivalry is a National Basketball Association (NBA) rivalry between the Philadelphia 76ers and the Boston Celtics.  The two teams have the most meetings in the NBA playoffs, playing each other in 19 series, with the Celtics winning 12 of them.  The 76ers are considered to be the Celtics' second greatest rival, after the Los Angeles Lakers. The National Basketball Association (NBA) playoffs are a best-of-seven elimination tournament among 16 teams in the Eastern Conference and Western Conference (called divisions, pre-1970), ultimately deciding the league's season champion in the NBA Finals. The 1983 NBA Playoffs was the postseason tournament of the National Basketball Association's 1982–83 season.  This was the final postseason using the 12-team format, before the NBA expanded the postseason to 16 teams the next season.  The tournament concluded with the Eastern Conference champion Philadelphia 76ers defeating the Western Conference champion Los Angeles Lakers 4 games to 0 in the NBA Finals.  Moses Malone was named NBA Finals MVP. The 2001 NBA Playoffs was the postseason tournament of the National Basketball Association's 2000-01 season.  The tournament concluded with the Western Conference champion Los Angeles Lakers defeating the Eastern Conference champion Philadelphia 76ers 4 games to 1.  Shaquille O'Neal was named NBA Finals MVP for the second straight year.  Since 2001, the 76ers have not advanced beyond the conference semifinals. The 1983 NBA Finals, also known as Showdown '83, was the championship round of the National Basketball Association (NBA)'s 1982–83 season, and the culmination of the season's playoffs.  It was the last NBA Championship Series completed before June 1.  The Eastern Conference champion Philadelphia 76ers defeated the Western Conference champion Los Angeles Lakers 4 games to 0.  76ers center Moses Malone was named as the NBA Finals Most Valuable Player (MVP). The Philadelphia 76ers are an American professional basketball team based in Philadelphia, Pennsylvania.  They are a member of the Atlantic Division of the Eastern Conference in the National Basketball Association (NBA).  Formerly known as the Syracuse Nationals, the 76ers joined the NBA when it was founded in 1949.  The Nationals had a record of 51–13 in their first NBA season under coach Al Cervi and won the Eastern Division crown.  The franchise were purchased by Philadelphian Irv Kosloff and Ike Richma in the spring of 1963; the NBA approved their franchise shift on May 22 and name change to the Philadelphia 76ers on August 6.  This brought professional basketball back to the city, which had been without a team since the Golden State Warriors left Philadelphia in 1962.  After coaching the 76ers since , Doug Collins resigned as head coach on April 18, 2013 following the 2012–13 season.  Brett Brown was hired to be the head coach of the 76ers on August 15, 2013 prior to the start of the 2013-14 season. The 1977 NBA World Championship Series was the championship round of the National Basketball Association (NBA)'s 1976–77 season, and the culmination of the season's playoffs.  The Western Conference champion Portland Trail Blazers played against the Eastern Conference champion Philadelphia 76ers, with the 76ers holding home-court advantage.  Their four regular season meetings had been split evenly, 2–2, with neither side winning away from home.  The series was played under a best-of-seven format, so the first team to win four games would win the series and become the league champions.
Answer: National Basketball Association (NBA) playoffs