What is why does he stare at me so intensely?

It's impossible to know exactly why someone is staring intensely without more context, but here are several possibilities:

• Attraction: They might be attracted to you and are showing it through intense eye contact. This could be romantic or platonic attraction. More information about this topic can be found on: Attraction

• Intimidation/Dominance: An intense stare can be used to assert power or intimidate someone. This is often accompanied by other body language cues like a rigid posture. Details about it are explained here: Intimidation

• Interest/Focus: They may be genuinely interested in what you're saying or doing, or simply deeply focused on you in that moment. More explanation can be found on this link: Interest

• Confusion/Curiosity: They might be confused by something you said or did, or simply curious about you. To get more information about this subject you can check: Curiosity

• Judgment/Disapproval: A stare could indicate disapproval or judgment. Look for other nonverbal cues to confirm this. More information: Judgment

• Thinking/Processing: The person could be lost in thought while gazing in your direction but not actually seeing you. This is often unintentional. Here's more about it: Thinking

• Unintentional Habit: Some people have a habit of staring without realizing it. It may have nothing to do with you personally.

• Neurological/Medical Reasons: In rare cases, staring can be a symptom of a medical condition.

Consider the context of the situation, your relationship with the person, and their typical behavior to better understand the reason behind the intense stare.