Facial perception is an individual's understanding and interpretation of the face. Just from looking at someone's face you can recognize their identity, gender, emotional state, intentions, genetic health, etc. Subliminal faces can influence mood, behavior, and facial expressions. I am always told by someone to "fix my face" because simply I cannot hide my emotions.
Facial detection: This means you have the ability to detect the location of a face in any image. This technique is mostly used for technology to identify human faces.
Facial recognition: This means you are able to compare faces and identify which faces belongs to which person. Facial recognition can identify human faces in images or videos, and determine if the face in two images belongs to the same person.
Emotion detection: This means you are able to classify the emotion on the face as happy, surprised, fear, sad, angry, irritated, etc. The most common way one can detect emotions from someone else is by analyzing the characteristics of their voice signal.
Facial detection can be important to use today because it is helping with facial analysis. I believe this has a huge impact on society today because not only does it help determine gender, age, or feelings but it is used in law enforcement, mobile technology, and banking and finances. Facial recognition is important to use because it does it's own work by verifying a person. By doing so, this is now providing you with accurate information and security. Emotion detection is important to use because you are able to recognize someone's emotions through their facial expressions. You can then use the information from their expressions to reveal their emotional state.