Licensing requirement for accessing read only SharePoint Online team site

If your user is not part of your organization, they can be invited to your SharePoint environment as an external user if your site collection is configred to allow that. If your user is part of your organization, I'm not sure if that user would have to be invited as an external user or if you'd have to pursue a higher license to get them in. Could you tell us if the user you have in mind is internal or external?