These keypoints mark important areas of the face: the eyes, corners of the mouth, the nose, etc. Facial Key Points (FKPs) detection is an important and challenging problem in the field of computer vision, which involves detecting FKPs like centers and corners of eyes, nose tip, etc.
Facial keypoints (also called facial landmarks) are the small magenta dots shown on each of the faces in the image above. In each training and test image, there is a single face and 68 keypoints, with coordinates (x, y), for that face.