Default Role in User Settings
Each user can have a default role defined in their user settings. (A default role is optional.)
Default Role As Access
When defining access, the user’s default role is the automatically selected option.
If someone modifies the default role of the user, this access definition will automatically be modified accordingly.
If a group is granted access using the default role, then each group member brings his/her own default role.
Sometimes it is easier to grant certain permissions locally to someone for a content item, without saving this permission set as a new generic role. In this case, when granting Access, select Custom from the pop-up, then click Save.
The permissions page will automatically open and you will be able to pick the necessary permissions as part of a custom role for the selected user/group. Click Save to store your changes.