It is a rendering program written at UCSD Bioengineering for use with continuity, but is generic and can be used with any application which can write to a socket. In order for continuity to be able to send data to the renderer, you must first open the data socket over which they communicate. This is and isn't true. Because these programs communicate over sockets there are no restrictions about which machines they can run on with respect to one another.
Continuity does all of the socket handling internally.
To change this, please see the commands section of this site. For the broad majority of users of this program, the default socket values will work fine.