What is meant by P-Q interval and S-Tinterval in electrocardiography?

In electrocardiography, P-Q interval (also called PR interval) is the time taken by the impulse to travel through atria, AV node and the rest of the conducting tissues. The normal PR interval lasts for about 0.16 s. The ST interval is the representation of time between the end of the spread of impulse through ventricles and its repolarisation.