[LAU] JACK: inputs and outputs

If I use qjackctl to start jackd, the connect window shows two capture ports and two playback ports. I can then start a pair of meterbridge dpms, and connect their inputs to the capture ports. Signal applied to the mic jack then shows up on the meters. So I deduce that the capture ports are related in some way to the mic jack. If I connect between the capture ports and the playback ports, should I then expect the signal to be present at either the headphone or the line output jack? And (this may actually be the same question), the soundcard has numerous analogue inputs (mic, line, CD), at least two outputs, not to mention whatever the mechanism in the digital domain is to relay internet radio etc. Can they all appear as ports in the qjackctl connect window? Is there some special imprecation needed when I start jackd? Thanks for your patience. Andrew.