What is the valve that separates the aorta from the heart? What is the importance of that valve?

The valve among the left ventricle and the aorta is the aortic valve. The aortic valve stops the retrograde flux of blood to the left ventricle during diastole. Besides, as the aortic valve closes during diastole, part of the retrograde blood flux is impelled by the coronary ostia (openings), orifices located in the aorta wall just after the valvular insertion and contiguous to the coronary circulation responsible for the blood supply of the cardiac tissues.

The Circulatory System - Image Diversity: coronary ostia coronary circulation