Why do girls stare at me all the time?

I'm finding that girls are staring at me quite often these days. It's kinda strange. They just look and I'm really shy and quiet.
I would think that if they were interested they would come say hello. But they don't. I'm very confused. I don't know how to read them. How to know if a Girl. How to Tell if a Girl Likes You?
Why do girls stare at me all the time?
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