What is a Deepfake and what risks does this technology entail?

If you have seen the movie "Rogue One: A Star Wars Story" you will know that we can see Carrie Fisher when she was young at one point in the movie, playing Princess Leia. But she is not Carrie Fisher as a young woman but a deepfake that imitates her. What uses do they have or what is it for? A deepfake is a video in which false images are shown where the face of a person appears in a situation that they have not experienced. Apparently real fake videos that have not happened but have been created by artificial intelligence and through machine learning techniques and deep learning algorithms capable of providing the face with the greatest possible realism.