It makes the connection appear completely lagless, since the Mosh client echos typed characters locally instead of waiting for a round-trip with the server. It

It makes the connection appear completely lagless, since the Mosh client echos typed characters locally instead of waiting for a round-trip with the server. It also buffers all command output server-side and doesn't send more output than the network connection allows. This means that even if you have a runaway process dumping lots of output, you can still immediately Ctrl+C it.