Great question!
I actually have not used the tone curve very much, though I probably should more.
I would consider it an advanced panel. It’s used for a lot of different things I think, though mainly adding contrast and removing color casts (both locally and globally). It’s extremely powerful and gives you ability to do things that aren’t available elsewhere in Lightroom, but it’s just a matter of understanding how to use it.
This article shows how it works, https://fshoq.com/a/lightroom-tone-curve-panel-tutorial
This video is also good, showing more details about how it works, https://www.youtube.com/watch?v=0-AYcQ6DKPw&list=PLllFqBuTM0WKjdQXb5XXKEMQmjseqic1J&index=7&t=0s
And this is a good video about how it’s used in real life situations, https://www.youtube.com/watch?v=z4qfMtJSwlI