CodeReviewer / collaborator server vs. client? Do I need both?

The downloads section has both a ccollab_server_9_5_9501_windows.exe and a ccollab_client_9_5_9501_windows.exe.
The installation instructions seem to implicitly assume that one should run the Server installation, and say nothing about the client.

What's the scoop here?

Edit:  after browsing through enough web pages here, I've reached the conclusion that the Server is necessary, but one can get away without the Client.  The client is used to interact with source code repositories, and upload files from them into the server.

But you don't need the client to do things like creating a review, or reviewing somebody else's code.

Somebody correct me if I'm wrong.