The fats and oils we consume everyday are, on the molecular level, made up of triglycerides. More broadly, these are ester compounds; organic substances derived from a reaction between an acid (usually carboxylic acid) and an alcohol. Triglycerides are made up of three fatty acid chains with a glycerol compound bonded at the end of the chains. The fatty acids themselves are usually classified into two species; which are unsaturated and saturated fatty acids. These names simply refer to the presence of double bonds among the carbon atoms. If there are any double bonds, the fatty acid is called unsaturated, while when no double bond is present, it is referred to as saturated. Now, while an individual fatty acid may be unsaturated, this does not necessarily mean that the whole chain of carbon atoms manifests double bonds rather than single ones. In a whole fatty acid chain, there is variation in the type of bond the various carbon atoms manifest. This is important because out of this variation arises grades of saturation or unsaturation. We can say that one fat is more unsaturated than the other because different fats have differing numbers of double bonds. A property that immediately rises out of unsaturation (double bond) is higher reactivity. The double bonds exhibited between some carbon atoms consists of one strong bond where the electrons are found half-way between the two nuclei, and a weak one where the electrons are further away from the two nuclei. Therefore, it becomes easier for electrophilic reagents to take over the weakly bonding electrons.
On the macro-level, these molecular characteristics (presence and concentration of double bonds or single bonds) naturally produce certain sensible characteristics, such as differences in color during reactions or higher and lower melting points depending on the degree of saturation/unsaturation. For example, when