Why did this guy stare and smile at me trying to make eye contact (his eyes light up too)?

We don’t know each other, just I’ve seen him around. I get a vibe that he likes me. Do guys give a girl a particular look that they like or love? Or is this just lust?
He checks me out too.
Why did this guy stare and smile at me trying to make eye contact (his eyes light up too)?
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