So, the simple explanation is this: Cholesterol is a necessary and important chemical, specifically, it is a sterol, and a precursor for Vitamin D, cortisol, estrogen, testosterone, and the substance that makes up the myelin sheath is. Cholesterol is not, and never will be, "the bad guy". Your body produces almost a gram of it a day, but dietary amounts are only about a third of that.

It it also the backbone of apolipoprotein, which is the actual thing your Doctor is talking about when they say "good cholesterol" and "bad cholesterol". Apo combined with other things (triglycerides and phospholipids) make HDL, LDL, and other familiar "cholesterol particles".

Since they shuttle fatty acids around, these fatty acids can be oxidized. When there are too many lipoprotein particles than your cells can safely clear, macrophages end up being targeted by the particles. Macrophages that take on too many damaged particles (damaged by the fatty acid oxidizing) can ram into arterial walls, which summons platelets to try to fix it.

The platelets use a calcium-based substance to fix the damage. Its sorta like organic concrete. Over a lifetime, your arteries become clogged with the concrete.

So.

The western diet and lifestyle lacks many important things required for healthy living. One of these is sufficient sun. Although Vitamin D supplementation is absolutely required for many people (most science is indicating that 2000 IU isn't even enough but is a bare minimum), we also have extremely little K2 in our diet compared to our ancestors, since it comes from certain fermented foods, and we largely no longer eat the correct fermented in sufficient amounts foods, even though it has been a staple of our diet at least 20 or 30 thousand years; long enough that it has changed our gut bacteria to basically necessitate it for many reasons.

K2 is required for signaling of arterial plaque removal, among other things. That organic concrete? It's not meant to be permanent, its meant to merely to stop you from potentially hemorrhaging.

Also, fun fact, anticoagulants that act as K2 antagonists (Warfarin, etc) lead to vastly increased arterial calcification (since, as an antagonist, it blocks K2 signaling). Those anticoagulants also can lead to brittle bones, because K2 is also used for signaling in a few biological processes that want to deposit the calcium in the right place.

So, I could just say "eat healthily", but nobody knows what the fuck that means. Beef liver and hard cheeses are good sources of K2, so is Sauerkraut and Kimchi. Supplement companies also sell good Vitamin K-focused multivitamins, many of which are a oil-filled gelcap with K1, K2 MK4, K2 MK7, and a meaningful D dosage (so its a drop in replacement for your daily D gelcap) (ex: Jarrow K-Right, but all the major good ones have a product like that).