delaySeen in ntpq output. How long it took for a time-request packet to be send, and the reply to be received.
offsetSeen in ntpq output. Also known as phase. How much your clock is behind (or ahead) of a certain clock.
jitterSeen in ntpq output. Also known as dispersion. The offset may jump back and forth e.g. not being constant. How much it does that is called the jitter.
ppm"Parts Per Million". For example 10 PPM means dat every 100 thousand seconds, the clock is one second off (almost 1 second per day).