The short answer is given here, in the organic molecule directory, alkenes page:
Squalene is found in shark liver oil, and is also a major component of the lipids on the surface of human skin. Although it is not obvious from the way the structure above is drawn, squalene is a precursor for the biosynthesis of cholesterol. Through a complex series of enzymatically controlled reactions, squalene is converted into an intermediate called lanosterol, which undergoes a number of subsequent reactions to become cholesterol.
Here is what the molecule looks like. Every angle or terminus has a carbon atom, with enough hydrogen atoms to fill the unused bonds up to carbon’s complement of four per atom. A double line indicates a double bond.