A Guest is a person who has access to the one project to which you’ve directly invited her/him. You can invite guests to collaborate on projects for free.
A Team Member is someone who's going to use Airstory with you or within your organization regularly. When you add team members to your Airstory account, you can access each other’s projects and the notes within them – but not until the project owner (which is not the same thing as the Team Administrator) explicitly adds the team member(s) to their project.
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Sharing Your Work with Team Members