A “match” (previously called "game instance") refers to a published game with its own scoreboard and invitation code. A published game can have multiple “matches”. For example, a weekend game might have separate matches for Saturday and Sunday. Each match would have a unique invitation code which players use to join the correct game, and players will be ranked on the scoreboard for that day/match.
If you have multiple matches and your game is published and set as "Listed in the app", players will join the most recent match.
Note: Whether the game is listed in the app or accessed via an invitation code, players are grouped into a match. For large games, we recommend creating separate matches to keep scoreboards manageable and easier to review.
Related article: Where can I find the scoreboard? – Locatify