What does it mean when a guy stares in your eyes for a really long time?

What does it mean when a guy stares in your eyes for a really long time?Ok well this happened twice and i dont know what it means, Please Help! When I talk to someone i like to make eye conact, but i was talking to this guy in my class but all of a sudden he was staring in my eyes(for like a really long time) and he wasn’t moving or talking . Then like 2 or 3 mintues later i turned around and he was still staring. The second time it was a different guy and he did the excatly the same thing and everyday i catch him staring at me, What does it mean????? Plz help sorry for it being so long