Hi!
HDL, or high density lipo-proteins, is a less harmful form of cholesterol that is found in the body.
There are two types of cholesterol:
1. LDL Low Density Lipo-Protein
2. HDL High Density Lipo-Protein
HDL is also referred to as 'good cholesterol'. HDL functions to redirect the cholesterol in the body back to the liver from where it is subsequently removed, where as LDL is more harmful form of cholesterol owing to the fact that elevated levels of LDL result in the deposition of cholesterol in the arteries.
Hope this helps!