This keeps getting brought up and it's simply not true. No, your phone isn't listening to you, plenty of tests have been done. It could easily be traceable with higher CPU usage, higher battery usage, network usage and so on, but there is zero difference between having a conversation next to your phone or the phone being in a literal sound proofed room.

Meta data, people you spend time with, what you look up online, your age, your hobbies, your interests, ads you have recently seen, location data, .. there's so much about you online that it's easy to predict.

And sometimes you talk about things because everyone else is talking about them. You're not that special.

It can be a bit scary how much you can predict about a person by just using a few simple facts (sex, age, location, income, ..).