Glycerol is one of the building blocks in lipids.It is a 3C alcohol.

The second structural unit is fatty acids.The all have a carboxylic acid group and a variable R group containing C and H.

Unsaturated fatty acids have double bonds (C=C).They have a low melting point and so tend to be liquid at normal temperatures.

Saturated fatty acids have no double bonds. They tend to be solid at normal temperatures.

Triglycerides are formed by condensation reactions between a glycerol and 3 fatty acids.These reactions form ester bonds.Triglycerides are not polymers.

Phospholipids are structurally different to triglycerides and have different biological functions.They have 2 fatty acid chains attached to glycerol.They have an inorganic phosphate group attached to glycerol in place of the third fatty acid chain.