The alpha (beginning) of a fatty acid is attached to a glycerol molecule. Three fatty acids attached equal a triglyceride, what we commonly know as a fat or oil molecule. We typically differentiate fats as being solid at room temperature and oils being liquid, but the structure of both is the same.
The omega (end) refers to the tail. The number following omega (3,5,6,7,9) when referring to unsaturated fats is how many carbons along you find the (first) double link, or bend in the chain, starting from the omega end.
This image is of a monounsaturated omega 9 fatty acid, oleic acid, found in olive and palm oil. Typically, carbon atoms are assumed where the bends are, and not shown.
The first carbon in the chain has two oxygens attached (shown in green), one of which is attached to a hydrogen atom (shown in red). This C-O-O-H arrangement is known as a carboxyl group, a way to recognize the omega end.
The only polyunsaturated omega 9 is mead acid, which the body creates out of oleic acid, when there is an omega 3 deficiency.
Only omega 3 and 6 are essential. This means they cannot be manufactured in the human body, and must be obtained through the diet. Omega 6 fatty acids are typically found to some extent in all edible vegetable and animal fats. Omega 3 fats are found in green leafy vegetables, in animal fats that have been pastured, in organic egg yolks, and in oily fish. Certain seeds are high in omega 3 fatty acids, particularly chia, flax and camelina. Oils from these seeds are excellent sources of omega 3 fatty acids.