Cholesterol is a waxy substance found in the body, essential for producing hormones, vitamin D, and bile acids. It is significant in nutrition because it exists in two main forms: LDL (low-density lipoprotein) and HDL (high-density lipoprotein). While LDL is often referred to as "bad cholesterol" due to its association with heart disease, HDL is considered "good cholesterol" as it helps transport excess cholesterol away from arteries. Maintaining a healthy balance between these two types is crucial for cardiovascular health.