If blood is going into the heart. The blood vessel is called the vein.
If the blood is comming out of the heart, the vessel is called an artery.
The technical term of the lung is pulmonary and the pulmonary artery takes blood from the heart to the lungs. The pulmonary vein takes blood from the lung to the heart.
The major artery in the body is the aorta. The major vein in the body is called the vena cava.
When the pressure is high, the blood forces down through the cuspds of the valve open and the blood flows through to a region to a region with low pressure which is the general rule for the valves and blood flow. On the other side of the same valve, if the high pressure area was lower than the low pressure area, such as when the ventricle contracts (the bicuspid/tricuspid valve) high pressure will get behind the cuspds and cause it to close which makes the heart sound - 'Lup' or 'Lub'. This is the first heart sound. The semi lunar valves also works the same way. When the pressure is high in the ventricle, it forces blood through to the artery, but when the heart relaxes blood flows backwards, closing the semi lunar valves making the second heart soun - 'dup'. Which makes the heart sound 'lup' (closure of the atrio ventricular valve) 'dup' (closure of the semi lunar valve) and this is the sound when you hear your heart beating.