Workspaces are just another of type of space. You can learn the difference between Organisations and Workspaces here: https://asana.com/guide/help/faq/common-questions#gl-workspace-or-org but we usually recommend opting for Organisations as they’re more flexible than workspaces!
No matter the space you choose (Workspace or Organisation), you can decide to use the free version (also called Basic) or to use one of our paid version (Premium, Business or Enterprise) . You can learn more about our different offers here: https://asana.com/pricing
If you’d like to discuss your own plan, I’d recommend reaching out directly to our support team who will be able to take a look into your account and advise you with the best solution for your team!