This is a pretty good description:

IFS is talk therapy in which you work with a therapist to identify and understand the specific sub-personalities or families that make up your internal mental system. Once you identify these parts, the therapist will help you acknowledge your feelings about these suppressed emotions, learn how to release these feelings so you are freer to address the actual problem, and ultimately find more positive ways to manage conflicts on your own. The therapist may suggest certain tools to help you do this, such as relaxation exercises, visualization, keeping a journal, and creating a chart that illustrates the relationship between Self and the different parts of you.