LDL stands for low-density lipoprotein. It's also sometimes called "bad" cholesterol. Lipoproteins are made of fat and protein. They carry cholesterol, triglycerides, and other fats, called lipids, in the blood to various parts of the body.
HDL stands for high-density lipoprotein. It's also sometimes called "good" cholesterol. Lipoproteins are made of fat and protein. They carry cholesterol, triglycerides, and other fats, called lipids, in the blood from other parts of your body to your liver.
If you eat unhealthy foods (trans fats, junk food, high in sodium etc) you increase LDL, blood pressure and systemic inflammation, if you do no exercise you decrease HDL levels. High LDL low HDL increase risk of heart disease because LDL gets oxidized and builds up under your blood vessel wall - curtain (the endothelium). This causes plaques that can break and cause clotting (thrombosis) leading to claudication, stroke or heart attacks.
When you eat an egg (including yolk) you eat a hefty amount of cholesterol, therefore increasing LDL in blood. But your body needs that, cholesterol - after all - stabilizes cell membranes and is used to produce many important hormones such as testosterone and estradiol.
So how many eggs are too many? Limit it to 1 - 2 yolks a day as your daily allowance of cholesterol. Eggs have a lot of cholesterol, you can eat more egg whites however.
So remember, HDL/LDL is produced inside the body, we just consume cholesterol which is then transported by these molecules.