what does it mean when a guy stares?

There's this guy and he used to stare at me all the time and when i would look he would look away and my friend said he was looking at me when i wasn't looking but today i went past him and i saw him and he didn't even look at me at all and he didn't come where we always hang round for lunch either does he hate me? but after that i like see him around and he still looks at me from a distance not just up close what do you think?