What does PR-Interval indicate on ECG truly ?

The period of time from the onset of the P wave to the beginning of the QRS complex is termed the P-R interval, which normally ranges from 0.12 to 0.20 seconds in duration.
The term “PQ interval” is preferred by some electrocardiographers because it is the period actually measured unless the Q wave is absent.
In contrast to common and old believe which PR interval represents the time take for the signal to move across from SA-node to AV node ,the PR interval spans the time required for the propagating impulse to advance from the atria through the AV node, bundle of His, bundle branches, and the system of Purkinje fibers until the ventricular myocardium begins to depolarize .It does not include the duration of conduction from the SA node to the right atrium (SA conduction).