At a minimum, most sites will have two security types; a Site Administrator and some type of Regular user.
Sites that use Public Projects will likely want to add a public security type and separate security types for Project Administrators can be very useful for control over administration rights.
You can create as many security types as required.
To add a new security type, click the New button. To modify a security type's settings, click on the security type name. To delete a security type, select the row by clicking anywhere to the right of the name and then click the Delete button.