Diet (exogenous source)
When you consume food from animal and plant sources, you will inevitably derive cholesterol from them. The cholesterol content of different food items vary. Some food items contain high quantities of cholesterol, such as meats, egg yolks, butter, and processed foods. Other foods will have a low quantity such as egg whites, fruits, vegetables, and whole grains. When you ingest meat, which contains high saturated fats, there will be an increase in the amount of cholesterol in your body.

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Produced in your body (endogenous production or source)
In your body, there are a number of biochemical processes that lead to the breakdown or production of cholesterol. Regardless of whether you are asleep or awake, these processes continue to take place. The biochemical processes that will lead to the production of cholesterol in your body are divided  into  5 stages:

Step 1—Mevalonate, when a six-carbon substance, is produced from acetyl coenzyme A.
The three basic nutrients that you consume every day are classified as; carbohydrates, fats, and proteins. These nutrients are complex in nature, which means they cannot be used readily by your body until they are broken down into their simplest components. The simplest components of carbohydrates are called glucose, that of fats are called fatty acids, and those in proteins are called amino acids. Thus, the simplest components of your basic nutrients are glucose, fatty acids,  and amino acids. These components of your foods cannot serve as sources of energy for your body until they are converted to the so-called acetyl coenzyme A, which subsequently gives rise to mevalonate,  which in turn, serves as the first step in the production of cholesterol in your body.

Step 2—Mevalonate forms active isoprenoid units
In the second stage, active isoprenoid units are formed from mevalonate. This is brought about by the addition of phosphate group to mevalonate. Without the phosphate group acquired by mevalonate, the process of producing cholesterol cannot proceed. So, where does the phosphate group come from? The substance which donates one phosphate group to mevalonate is the so-called adenosine triphosphate (ATP). The ATPs are the ultimate sources of energy needed by your cells. Without them, the different biochemical processes in your body cannot proceed,  and your life will cease to exist.

Step 3— Six isoprenoid units form squalene. The isoprenoid units produced in step 2 combine together to form squalene.
Step 4—Squalene is converted to lanosterol.
Step 5—Lanosterol is converted to cholesterol.

Transportation of body cholesterol
The cholesterol molecules in your body need to move and transfer from one tissue to another. In doing this, they ride on a substance called lipoprotein. These lipoproteins are combinations of fats and proteins, and they are classified into four classes: chylomicrons, very low-density lipoproteins (VLDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL). The chylomicrons and the  VLDL  transport one form of fats which is collectively referred to as triglycerides, while the LDL and the HDL transport 70% and 25% of your plasma cholesterol, respectively.
The LDL carry and bring your cholesterol away from your liver—that is, they bring your cholesterol towards the peripheral tissues, such as your muscles, heart, and blood vessels. When that is done, it is possible that some of the cholesterol is deposited in the walls of your blood vessels, leading to the development of atherosclerosis. When atherosclerosis develops in the small blood vessels of your heart, you may develop coronary heart disease, which could lead to myocardial infarction or heart attack. For all of these fatal and bad consequences, the LDL is branded as the bad cholesterol. The HDL, on the other hand, carry cholesterol away from your peripheral tissues and bring them back to your liver for elimination. Due to this action, the amount of cholesterol that could have been deposited in your peripheral tissues is reduced considerably, preventing the development of atherosclerosis and coronary heart disease. For this beneficial action, HDL is branded as good cholesterol, as it facilitates the so-called reverse cholesterol transport, whose endpoint is the elimination of cholesterol.

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