Help me understand Voice Recognition tech

I am interested in getting an app that would allow me to make notes via voice-to-text. I work in a field with HIPAA protections. I'm having trouble figuring out the nuances of privacy related to these apps.

First off, is this kind of software considered "AI"? How does it even recognize that a sound equals a word? Do they use LLM tech? Does the tech learn to recognize my voice better over time? Does it use my recordings to learn to understand other's voices? Is this all a black box? How can I take precautions such that no one except me hears the things I transcribe?

This is just such confusing tech! It seems like it's fairly old and common but the more I think about it in relation to current age AI, the more creeped out I get! And yet my doctor uses one regularly... I'll be asking her about it too, don't worry.

Thank you!