The following is merely a soupçon of what exists on that page:
A Great discussion of olive oil chemistry by Guido Costa in simple terms
Herewith my contribution on FATTY ACIDS AND ACIDITY: Olive oil is composed mainly of triacylglycerols (triglycerides). Chemically speaking, these are molecules derived from the natural esterification of three fatty acid molecules with a glycerol molecule. The glycerol molecule can simplistically be seen as an "E-shaped" molecule, with the fatty acids in turn resembling longish hydrocarbon chains, varying (in the case of olive oil) from about 14 to 24 carbons atoms in length. Thus the triacylglycerols can, for our purpose, be visualized as elongated E-shaped molecules, each with three long extensions, being the three fatty acid chains "attached to each horizontal bar of the E".
Please note that we are dealing here with fatty acids forming part of the triacylglycerols molecule. They are distinct from FREE FATTY ACIDS, which we'll talk about later!
Various fatty acids are found in nature. They differ in length (number of carbon atoms in the chain) as well as in the type of chemical bonds found within the chain. Mostly these carbon-carbon bonds in the chain are "single" bonds, comprising 2 electrons shared between adjacent carbon atoms. However, in certain of the fatty acids, some of the bonds are "double bonds", where 4 electrons are shared between adjacent carbon atoms. The fatty acids that have no double bonds in their chains are called "saturated" fatty acids (all the carbons in their carbon chain are "saturated" by hydrogen atoms). Examples of saturated fatty acids are Palmitic Acid (16 carbons long), Stearic Acid (18 carbons long) and Arachidic Acid (20 carbons long). The fatty acids that have one carbon-carbon double bond somewhere along their length are called monounsaturated fatty acids (one carbon-carbon bond which is not fully saturated with hydrogens), i.e. one of the bonds available at each of 2 adjacent carbons is now used to form a double bond between themselves instead of being used to bond externally to hydrogen atoms. Examples of monounsaturated fatty acids are Palmitoleic Acid (16 carbons long) and our famous Oleic Acid (18 carbons long). Oleic acid is the most abundant fatty acid found in nature. The double bond in Oleic acid occurs in the mid position of the molecule, between carbon 9 and carbon 10.
I don't want to make this sound too complicated, but as soon as one brings a double bond into the picture, one must bear in mind that...