Why is this guy acting like this?

this guy is in my university and v share same block thou he is not my class fellow,(me doing bachelors and he's doing masters), its been 4 months.. I noticed him noticing me, and his friends (3-4 girls and 2 of his guys) use to notice me as if I have done something :/ when ever I pass by them ( this thing really confused me!) at times I fell as if there's some thing wrong with me that's why the are all looking like this :/ .. long story short.. at times he totally ignores me, and other time he is always in vicinity, standing where he could see me and his body is pointing towards my direction when ever I look at him half of the times he is already looking and stares back and I am the one turning mi gaze away also at times he is smiling with dimples while looking and have some thing in his eyes. likes