The sitecore\Sitecore Client Securing
role grants access to features and applications used to assign access rights.
Gives the user access rights to security features in the Content Editor and other relevant applications.
This role is intended for users who need to maintain users and access rights.
You need to assign the sitecore\Sitecore Client Account Managing
role in order to provide access to applications used to maintain users, roles, and domains.
Gives the user access to maintain users, roles, and domains in the Access Manager, the Domain Manager, the Role Manager, and the User Manager.
Both sitecore\Sitecore Client Securing
and sitecore\Sitecore Client Account Managing
are members of the sitecore\Sitecore Local Administrators
role.
These roles are described on the Security Roles Sitecore official documentation page: