What is the significance of essential hypotension?

Varies. Essential means that it is not secondary to some known cause such as bleeding, dehydration, or an underactive adrenal gland. So if your blood pressure is lower than average it might be said you have essential hypotension. If you feel well, no problem. In fact those with a low BP live longer. There may be some who just feel weak and dizzy with low bp. Sort of a vague not well understood problem, .
Cause unknown. Essential means "cause unknown". Hypotension means "low blood pressure".