Protein powder concentrates are made by extracting protein from the source material through the use of heat or enzymes. In the case of whey protein, this removes water, some lactose, and minerals. Protein concentrates tend to have a lower percentage of protein as compared to isolates because they still contain some carbohydrates and fat.
Protein isolates are made by filtering out most of the impurities found in concentrate, including lactose which makes this product far easier to digest. This creates a more pure product that has around 90% protein content.