Here's a breakdown:

* Saturated fatty acids: Have no double bonds between carbon atoms in their hydrocarbon chain. They are typically solid at room temperature.

* Unsaturated fatty acids: Have one or more double bonds between carbon atoms in their hydrocarbon chain. These double bonds can be in either a *cis* or *trans* configuration. They are typically liquid at room temperature.

Monounsaturated fatty acids have one double bond, while polyunsaturated fatty acids have two or more double bonds.