Users will need at least one "access CLIENTNAME tickets" permission and "create tickets" permission to be able to create tickets.
Users can only create and update tickets for clients they can access.
Users with "can suppress notification" permissions have the option to manually disable a notification email from being sent out. An email will still get sent to admins telling them that an update has been made but not showing the contents of the update. This feature allows passwords and other sensitive information to be added to tickets without being sent out as a plain text email.
Users with "can assign tickets to self" permissions are able to assign a ticket to themselves, or to assign the ticket to nobody.
Users with "can assign tickets to any user" permissions are able to assign a ticket to themselves or to another user. Only users with permission to view a given ticket can be assigned to it.
Users with "can subscribe other users to notifications" permissions are able to subscribe other users to email notifications when a ticket is updated. Users without this permission can only subscribe themselves. Only users with permission to view a given ticket can be subscribed to notifications for it.
Users with "download mail via support/fetch" permissions can access the path "support/fetch" which will cause the Support module to download all client email. Mail is also fetched when Drupal's cron is run, but this allows mail to be checked at a different frequency than cron is run, if desired. If you are using Support's mail integration features and you are running Drupal's cron, you do not ever need to access support/fetch.
Users with "view other users tickets" permissions can view all tickets for any client that they have "access CLIENTNAME tickets" permissions. Users that do not have this permission can only view tickets that they themselves have created. Users with "administer support", "edit any ticket" and/or "delete any ticket" permissions can always "view other users tickets" whether or not they are explicitly granted this permission.
Users with "edit multiple tickets" permissions will be able to add updates and change the state and priority of multiple tickets from the client overview pages.
When creating and modifying tickets, users with "can select client" permissions can assign the ticket to any client that they have permission to access tickets for.
When creating and modifying tickets, users with "can select priority" permissions can set the priority of the ticket.
When creating and modifying tickets, users with "can select state" permissions can set the state that the ticket is currently in, based on the workflow defined in the support_states database table. By default, this means that new tickets must be in the 'new' state, and only upon updating a ticket can the user set the state to 'active', 'pending', or 'closed'.
Users with "can administer state" permissions can change the state of any ticket from any state to any other state, ignoring the workflow defined in the support_states database table.
Users with "move ticket" permissions and permission to edit a ticket see a new "Support ticket" fieldset with a "Move ticket" field allowing them to specify a parent node id which will cause the ticket and any updates to be moved and become updates on the specified node id. Note that this only allows for moving an entire ticket and all its updates, not specific updates.
Users with "administer support" permissions can access and update all clients and client tickets, and automatically have all support permissions available to them.