The full form of POG is play of the game
“POG” is often used in gaming to mean “play of the game.”

Before the spread of the internet and gaming culture, “pog” was a small, circular piece of cardboard commonly used to play a game by children and young adults in the 1990s.

“POG” can also be used with “champ” to make “POGChamp.” This is sort of an abbreviation for “play of game champion.” This means that the player performed extremely well in a match and will be the best player in the game and get the “play of the game.”

Conversation Examples
Here are a few examples:

Example 1:
Gaming Streamer: Live stream starts in 15 minutes. Check out my sick plays and the road to the finals. My goal is to get POG three times today.
Stream Watcher 1: Yeah man, go get ’em!
Stream Watcher 2: Can’t way, gonna be #pogchamp for sure!