Group of users and roles

Hello everyone,
Can anyone explain to me the difference between user groups and roles? I understand that a whole group can be assigned a role. But what is the point of adding a user to a group with a specific role or assigning the same role to just a user

A group can be assigned one or several roles.
This can simplify the management of authorizations.
Use what makes sense for your application and your organization.
https://docs.axelor.com/adk/5.4/dev-guide/modules/security.html