What does it mean when a guy stares at you without smiling?

If you are sitting in the cafeteria and this guy you don't know just catches your eye contact and then u stare at each other intensely and then u look away but when you check back he is still staring at you, (this is a very long sentence 😂) what does this mean? IDK if that means he is not interested or he likes you too or he is in lalala land!... thank u for the help