The two parts of a fatty acid are:

• A hydrocarbon (acyl) chain, which is a long chain of carbon and hydrogen atoms. This chain can be saturated (single bonds only) or unsaturated (one or more double bonds), and it determines the fatty acid's properties such as fluidity and melting point.
• A carboxyl group (-COOH) at one end of the chain, which is acidic and polar, giving the fatty acid its name and chemical reactivity

In summary, a fatty acid consists of a hydrophobic hydrocarbon tail and a hydrophilic carboxyl head.