What is the difference between heart rate and ventricular rate?

On an ECG the heart rate will match both ventricular rate and atrial rate if the heart is normal. If people have atrial fibrilation then the ventricular rate will be used on the ECG to work out the rate of the ventricular contraction and vice-versa with ventricular fibrilation. Usually both atrial and ventricular rates match so if the atria contracts at 70 BPM the ventricles will beat at 70 BPM. It is possible for the ECG machine to work out atrial or ventricular rate if needs be. Usually, however, if the ECG machine just displays heart rate then both ventricular and atrial rates match.