Fish oils are a source of omega 3, a fatty acid considered essential for the proper functioning of your body. It is considered essential because your body does not have a way of manufacturing this oil from other dietary nutrients. Except for the essential fatty acids (omega 3 and 6), your body can very efficiently build most fatty acids from sugar (eg. Cholesterol from glucose).
Omega 3’s can be found in some nuts and seeds as well as sea foods (with fatty fish like salmon containing the highest amounts).The Omega 3 oil is then converted into two other components (EPA & DHA) by our body. This process of conversion which is neither efficient nor adequate is what necessitates supplementation specifically with EPA and DHA and not just any Omega 3! What is important to note here is that vegetarian sources of Omega 3’s don’t contain neither EPA nor DHA. In other words, nuts and seeds can only provide the raw materials for our body to manufacture EPA and DHA, whereas meat sources of Omega 3 naturally contain EPA and DHA.
What’s so special about EPA and DHA you ask?
EPA and DHA have anti-inflammatory properties. While the typical Western diet has a much greater ratio of Omega 6 compared with Omega 3, research has shown that by increasing the ratio of Omega 3 to Omega 6 in the diet, and consequently favoring the production of EPA in the body -or by increasing the dietary intake of EPA and DHA through consumption of fatty fish or fish-oil supplements- reductions may be achieved in the incidence of many chronic diseases that involve inflammatory processes; most notably, these include cardiovascular diseases, inflammatory bowel disease (IBD), cancer, and rheumatoid arthritis, skin conditions as well as psychiatric and neurodegenerative illnesses.
Some may argue that humanity has lived just fine without the supplementation of fish oils. That argument however was null the moment humanity stopped being hunters and gatherers!
Genetically our bodies function optimally on the paleolithic diet of hunters and gatherers of ages past. 
Unfortunately, evolution takes millennia and evolutionarily speaking our civilization and way of living and functioning has changed so dramatically over the past thousands of years without the necessary adjustments in our genes (to deal with the changes in our environment, diet, and way of living). Hence we’ve got bodies primed for a paleolithic diet and actual diets of processed foods, filled with grains, and vegetable oils causing havoc on our system. Add to that our toxic laden oceans where for safety reasons there’s a cap on fish consumption! Solution? Fish oil supplementation.
An article on the Paleolithic diet and the research proving it fit to our genetics and its health benefits for the chronic diseases of today to follow!
When supplementing with Omega 3’s however, 
always keep in mind that without a good amount of EPA and DHA you’re not actually obtaining much benefit from supplementation. Also, you should be consuming only pharmaceutical grade fish oils made from small fish (anchovies and sardines). Small fish have the lowest amount of heavy metals and most reputable laboratories ensure removal of toxins and heavy metals.
ALWAYS READ YOUR LABELS!
