A: Think about restaurant business. You have a kitchen that's your internal collaboration - The workspace. In restaurant you also have a dining area - That's the portal. You don't want as a professional service provider invite your clients to the kitchen where they see all the mess. And that's what happens with many businesses. You use workspace to work with your team and when it comes to deliver information and collaborate with your clients you use portals. Portals and workspaces are the same level of hierarchy. On AppSumo page there is a Youtube video please watch it. It gives the idea of the concept.