The Left Anterior Descending coronary artery is the one that supplies blood to the largest and most important pumping muscle section of your heart; ie the Anterior Wall of the Left Ventricle.
You can have blockages in any of the coronary arteries or their branches thereof, but certain arteries are more important than others. Sort of like gun shot wound to the leg, you'll probably live, gsw to the head, you'll probably die? Heart attack
from blockage to the Right Coronary Artery
(RCA) or Left Circumflex (LCx) and you'll probably live; heart attack from blocked LAD, you'll probably die. The worst one is a blocked Left main Coronary Artery (before it divides into the LAD and LCx). A blockage there knocks out the Anterior, Lateral, and parts of the Posterior wall of the Left Ventricle. Inotherwords, your left ventricle is no longer supplied with blood. That one is referred to as a widow-maker because a patient so afflicted will almost surely die.
This is obviously a gross over simplification, but there it is in a nutshell.
You need to talk with your doctors to find out where you have blockages and what your best options are.