Difference between and stalker and someone who is pursuing?

What do you say is the difference between someone who's a stalker or someone who is pursuing?

In my mind a stalker is unknown (anonymous), knows things he/she shouldn't or continues to pursue when he/she has been asked to stop, move on, given warning.

Someone pursuing is putting themselves out there, persisting, trying to make the other person like them.
Difference between and stalker and someone who is pursuing?
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