By default, if you configure an agent as a 'Dialler Agent', you can assign them to a single OUTBOUND agent group only; and you cannot assign them to inbound agent groups.
If you have storm's blended functionality enabled, you are able to assign 'Dialler Agent' agents to any number of agent groups, and they can be inbound agent groups or OUTBOUND agent groups. Queue priority settings and blended pacing (controlled using the queue's matching rule Time since agent available (seconds) setting) then control how call routing is handled when a campaign is run that uses agents assigned to inbound and to OUTBOUND agent groups.
For more details about blended configurations see the Blending section of this document.