According to the Sitecore XM Cloud Documentation for Developers1, security roles define how different users access different types of records in Sitecore. To control access to data and resources, you can create or modify security roles and change the security roles that are assigned to your users. A user can have multiple security roles. Security role privileges are cumulative.Users are granted the privileges that are available in each role that's assigned to them2.
This makes it easier for you to manage your security system because you do not necessarily have to assign access rights for each item in your content tree.Instead, you only need to assign and manage the access rights on the parent items and then specify whether their descendants can inherit these access rights3.