A "competition" may have multiple "seasons".
A "season" may have multiple "stages"
A "stage" may have multiple "groups"
A "group" may have multiple "rounds"
There may be multiple "matches" in each round

For example:

The World Cup is a "competition"
It has seasons 2022, 2014, 2018, etc.
There will be group stages in the 2022 season
Each group will have 3 rounds
There will be multiple matches in each round