Clients are people/organizations for whom projects are done. Client accounts are different from user accounts in that they are free and hence have limited functionality and Celoxis does not notify clients when their accounts are created. You must inform clients. Clients can view their projects, check project status, participate in shared discussions and upload/download documents shared with them. You can further limit what the client can see/do. A special client (Internal) is created by default which can be used for internal projects.
To create your clients, please read the Add/Edit/Delete Client section of the User Guide.
Client accounts are FREE irrespective of whether they have a login or not.