Earlier quoted context omitted.
With on-line music sessions now spanning the globe, and only a small minority of people able to achieve perfect absolute pitch, standard pitch is the lingua franca of internet music, and should be widely useful.
What is standard pitch?
Most people that tune by ear tune relatively, e.g. they tune each string to another string. If there's no standard reference then it'll sound fine but you can't play with anyone else who is tuned to the standard... Though many people can tune to a reference pitch as well without using a tuner.