what is omega 3 fish oil good for?!

Fish Oil helps a bit with joints, but it's one of several things that may be needed depending on why your joints are hurting... if they still hurt regularly, you may be lacking something else.
Think of it this way, if your car's engine is making a weird squeaking noise, would you just put a couple drops of some random oil on it and call it good? No, you'd make sure to put the right type of oil in the right spot to stop the squeaking. Same with your joints (or any other part of your body)... if your body is deficient on a certain nutrient and you don't give your body the right nutrition it's lacking, it won't correct the problem.

If the Fish Oil isn't helping as much, you could also try one of several options like Microlactin, Tart Cherries, Glucosamine, Chondroitin, MSM, Hyaluronic Acid, Danish Rose Hips, and/or Bromelain. Glucosamine, Chondroitin, and MSM are commonly in combinations together because they work for similar aspects of joint health (and most recommend 1500 mg of Glucosamine, 1200 of Chondroitin, and various levels of MSM spread throughout the day) so that would probably be a good place to start. The down side is that those take the longest to work because they are the main nutrients that your body uses to create new cartilage, but because of that, they work the best in the long run.
The only thing to really watch out for is allergies. Glucosamine is typically from Shellfish and Microlactin is from milk. As long as you're not allergic to those, you should have no problem and you could safely take any number of those together.

Also, you could keep taking the Fish Oil because that has benefits for skin health, cardiovascular health, brain health, eye health, and heart health in addition to the minor joint health benefits. ;-) Good luck and I hope I helped!

Health/nutrition classes, personal experience with several of those products, and personal research in my role as a Product Specialist for a vitamin company

I take Omega 3 for my OCD. It can help with brain function but it is really good for cardiovascular health. I've taken it for years and I've felt good. No bad side effects. I think it's a good supplement to take! :)

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Omega 3 is an essential fatty acid (omega 6 is also essential) which our body cannot produce, meaning we need to supplement it or obtain from external source. There is increasing evidence in recent years on the health benefits of omega 3. It is linked to heart health and autoimmune disease, such as rheumatoid arthritis, and many other health conditions. That's why one of the earlier answer by someone mentioned about lubricating joints and sockets. Omega 3 doesn't 'lubricate' the joint. Most joint pains are caused by inflammation. Rheumatoid arthritis is one such inflammatory disease. There are plenty of research done regarding the efficacy of omega 3 and inflammation.
In our modern diet, we consume way too much omega 6. The more balanced ratio of omega 3 to omega 6 should be any where from 1:1 to about 1:4. BUT, our modern day diet has skewed the ratio to 1:26. When the ratio is skewed like this, what does that mean?
It means our body cannot handle inflammation effectively and correctly. Let's use a recent example which nearly reached epidemic level. The H1N1 crisis really illustrate this point well. When a person is infected with H1N1, the body responds by sending 'armies' to fight the infected area. This part of the 'army' function is primarily due to the indirect level of omega 6 in our body. This defense reaction (i.e. body sending 'troops' to fight the infection from H1N1) is good and also a proper immune system response. However, because our body's ratio of omega 3 to omega 6 is so skewed that the 'troops' do not know when to stopped their needed action, i.e. defense. In other words, these 'troops' are overdoing what they were supposed to do. This is known as cytokine storm in scientific term. Anyway, the 'troops' were waiting for body signal to stop what they were doing. That signal relies on the level of omega 3 in the body. IN short, people died from H1N1 were not killed by the H1N1, but rather by the overreaction of the imbalanced immune system of the body. That's why H1N1 victims were mostly died from pneumnia in their lungs.
Sources of omega 3 are mostly fishes. One plant or rather seed that has a good ratio of omega 3 to omega 6 is flaxseed.

I have read about essential fatty acids a lot due to my job as health product development as well as my involvement in arthritis, cancer and other lifestyle diseases. One good source of such information is Dr Weil's website (www.drweil.com). I am not affiliated or have any connection to Dr Weil. But in my job, I have learned a lot of helpful information from Dr Weil. It's definitely worth visiting his site for helpful information.