Question

If I use ssh -X to run an application from Computer A on the screen of Computer B, how are the computation and resources divided up between the two computer's processors?

• Sometimes the audio will play on Computer B, for instance, and sometimes it will play on Computer A, depending on configuration
• Anything that depends on DBus won't work over the connection.
• Text editor Open... dialog sees the files on Computer A

It's kind of confusing.

Also, which is the "server" and which is the "client"?

Answer 1

The computer that displays the application on its monitor (computer B) is the X server. The other computer (A) is the ssh server. What is the server depends on the context, but personally, I would usually mention the ssh server (A) as the “server”.

Computer B uses some resources to draw the windows (and if you have configured it: play sound), while computer A will do all other computation.

Usually, computer B's work requires less resources than computer A's. Computer A will do most of the work, and just send the results to B: Draw a line here, color this area black, etc.

Read the article X Window System at Wikipedia to learn more about X servers and clients.