Going into detail on what this term means and how it relates to health guidelines. This article may be incomplete.
There are typically 3 major arteries that supply blood flow to the heart muscle. The left main is a short stubby "tree trunk-like" vessel that originates from the left coronary cusp of the aorta where it plugs into the heart. It then gives off the left anterior descending (LAD) artery which runs over the top (anteroseptal) of the left ventricle (pumps to body) and the left circumflex (LCX) which supplies the lateral wall (arm pit side) of the heart. The right coronary artery originates from the right coronary cusp of the aorta and supplies the right ventricle (pumps to lungs) and wraps around and supplies the underside (inferior) wall of the left ventricle in 85% of us. In 15%, the LCX comes all the way around and supplies the bottom of the left ventricle. There are other less common anatomical variations but essentially, all walls of the heart are properly supplied with blood flow by the coronary arteries.