Yes, never experienced talking about a subject and seeing an ad about that same subject a few hours or days later?
Yes, your phone is listening to you.
Google at least has the decency to offer you to delete these recordings. Cough cough, not that I believe they didn't already compute what is in the conversation but at least it is there.
https://myactivity.google.com/myactivity?utm_source=help&restrict=vaa
Cheers,
GD