Here are some pictures of some good squats and some bad squats. These are all paid actors so no judgement necessary.
Good Squat. Weight on the heels. Neutral alignment in the spine. Hip crease below the knee.
Loaded knees, hips dropped first. Weight on toes. Rounded back. Funny facial expression. Thanks Willy
This squat looks funny, but it is surprisingly common. This happens when you let the chest fall too quickly. When the chest falls faster then the hips you never quite hit the pocket of the squat. Very common when you get tired. Quick fix is keep the hands up and elevate the chest!