When a guy acts like you dont exist or ignores you? What does it mean?

Anonymous
What does it mean when a guy you see on a regular basis (like twice a week) never starts a convo with you or talks to you unless you are by yourself? Like if im around other people he won't even look at me unless i say something he kind of makes it seem like i dont exist. But if im by myself he will come up to me and talk to me. Or if he's driving me home (If someone tells him to give me a ride) he will of course start up a convo with me. He once asked me if I had a boyfriend and then asked me about my ideas on marrige and when I wanted to get married. But I don't know its kind of werid.. maybe im wrong...
When a guy acts like you dont exist or ignores you? What does it mean?
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