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Veritasium did a pretty good video on some of them: https://www.youtube.com/watch?v=GVsUOuSjvcg

That video is about analog computers

The video is about analog chips for ML/NNs. His profile of this company was particularly interesting: https://mythic.ai/

OP asked about chips for AI.

Do companies pay him or does he do these ads for free?

He gets paid. It says so at the start of the video, but I guess that could depend on where you live.