The regional championships take place during the Elite Eight stage of the March Madness tournament. There are four regional championships each year, for each of the four regions: East, South, Midwest and West.
The terms 'Elite Eight' and 'Regional Championship' are used interchangeably.
When the Round of 64 begins, there are 16 teams in each region. By the Elite Eight, there are two teams left in each region. The two remaining teams in each region play each other. If a team wins in the Elite Eight, they advance to the Final Four.
The regional championships take place in new locations from year to year. However, the games will be played in the corresponding region. For example, the Midwest regional championship will be played somewhere in the Midwest.
The regional championships are very important, and viewed by millions of people. They can also deliver some amazing matchups. In 2018, Kansas faced off against Duke in the Elite Eight in what would go down as an OT thriller. The ratings of this game, on CBS, hit an all time high of 9.2/10. 15.44 million people viewed the game on CBS, which was actually 3% lower than the UNC and Kentucky Elite Eight tilt from the year before.