A fatty acid can be either saturated or unsaturated. A saturated fatty acid or Palmitic Acid, has carbon atom that have single bonds where they share a set of electrons. Due to this, there is two hydrogen atoms for every oxygen.
An unsaturated fatty acid on the other hand has one or more double bonds. This means that a carbon atom is bonded to another carbon atom and they together share two sets of electrons. This is opposed to being bonded to hydrogen atoms. An unsaturated fatty acid is also known as Oleic acid. (C18H3402)