Can I invite users only from my company or also from outside my company?

Yes! As Organisation Owner or Administrator you can invite any User to your platform. Depending on their set Role, they are able either to invite other Users as well or not. For example:

•  You invited new User as Domain Administrator - he or she will be able to invite other Users only to permitted domains
  
  
• You invited New User as Product Administrator - he or she will be able to invite other Users to the same product with access to all its resources
  
  
• You invited a New User as Domain Editor - he or she will not be able to invite new users to permitted domains.