Why do you stare at other people?

What is the main reason for you to stare at someone?

I have that feeling, and I was told by someone looking from the side, there is someone at my workplace, staring at me quite a bit. But when I turn my head, she immediately change direction so I will not see her doing that.

Interpretation of this behavior is not clear to me. Why stare? Why not just walk, talk, ask? The truth, that makes me feel not so good, maybe something wrong with me.

Staring is such behavior that is not successful in my opinion, especially that you can give it many interpretations. What is your main reason? I try to avoid this kind of thing.