Butter typically goes through homogenization which means that the milk that is used goes through a certain process which is used to reduce some of the fat in it. Usually butter is made from pasteurized cream which is a different process entirely. The homogenization process involved grinding the cream into small particles so that the cream is not able to rise to the top. Most milk is homogenized in order to completely purify it as well as for removing fat.
Organic butter is generally better for you because it is not processed and contains little to no fat. Those who are serious about staying healthy while still enjoying milk will want to try their best to purchase the organic kind. Even though it may be a bit more expensive, it will still be healthier for you overall.