If you were looking for the mark on a Pokémon's status screen that indicates which game it came from, see Origin mark.
A mark (Japanese: あかしmark) is a special marking that a Pokémon can have when caught that was introduced in Generation VIII. As with Ribbons, they are shown on a Pokémon's summary screen and grant a particular title to a Pokémon that is shown when it is sent out in battle. However, unlike Ribbons, a mark cannot be earned by any Pokémon—it is already set when a Pokémon is caught.
Approximately 5% of Pokémon encountered in the wild will have a mark. Any Pokémon obtained after cooking curry while camping will have the Curry Mark. Pokémon hatched from Eggs or caught in a Max Raid Battle will never have a mark, so it is currently impossible to have a Pokémon with both a Hidden Ability and a mark.
For weatherless wild encounters, of the 5% that have a mark:
Approximately 40% will have the Uncommon mark
Approximately 40% will have a time-based mark
Approximately 20% will have one of marks 69-97
List of marks
A mark for a peckish Pokémon.
Good chance in the afternoon (12:00 p.m to 6:59 p.m.)