One key thing to understand is that Users can be given different Roles and that each Role will have its own specific set of Permissions, which determine what a User can do, and what they can see.
Another key thing is the integration between Drupal Users and CiviCRM Contacts.
When a Drupal User is created, a CiviCRM record is automatically created. However the reverse is not the case. Creating a CiviCRM contact does not created a Drupal Account for them.
And when it comes to deleting a contact, deleting the CiviCRM record does not - yet - delete the Drupal account, or vice versa.
The critical element that ties Drupal and CiviCRM together is the email address.
So, if a person has a CiviCRM record, but no Drupal Account, then you need to create a new Drupal User, and paste in to the form the email address from CiviCRM - this will link the two records.
Drupal accounts for multiple CiviCRM contacts can be created using the User Import feature.
There are some basic Roles that all Drupal systems have, and some which have been created for this site.
- Anonymous - this is anyone who is visiting the site withou having logged in
- Authorised - this is anyone who is logged in
- Administrator - someone who has access to all functions on the site
There will then also be series of roles to give specific permissions to various functions on Drupal and CiviCRM.