A division is used as a "Folder" to hold a list of all the teams and/or players of one group. That list then goes into Round-Robin groups or Brackets.
Divisions in a League:
For example: You create an event called: D&R Star Pool League 2019-2020.
Under that event, you create Divisions: ex. Rochester Monday 4 person, Wednesday 8 ball, Thursday Singles League, Monday Fall League, etc.
Divisions in a Tournament:
For example: You create an Event called: Las Vegas VNEA Championships 2020
Under that event, you create Divisions: ex. Open 8 ball, Mixed 9 ball, Ladies 9 balls, etc.