English SharePoint Online provides cloud base SharePoint portal to the subscriber. Whether you subscribe Enterprise plan that allow many internal users or Small Business plan starting with 1 to 20 users, you always be able to invite external user. This scenario is very useful when you build a start-up company and decide to use SharePoint Online for your portal. You can start with very cheap subscription of 1 user as the company administrator, and invite other staff as external user to the site.