Two years into its run on CBS, Match Game spawned an evening edition which, like the daytime show, ran for six years. Match Game PM (so named because the daytime show might've been airing in the morning in some cities as opposed to the afternoon) was a weekly, ah, bonus for fans who were unable to watch the network version.
The biggest difference is that each episode is self-contained, with no returning champions. Beginning in the 2nd season, a 3rd round of game play was added to fill time, eliminating the prospect of dead air, in a way.
The comedy aspects were ramped up in this version, as you'll see in this 1976 episode, in which Richard Dawson and Betty White impersonate fellow panelists Brett Somers and Charles Nelson Reilly, respectively.
Four years in, CBS cancelled the daytime Match Game, which moved into syndication. Subsequently, PM was given the heave-ho after its 6th season.