https://www.musical-u.com/learn/finding-the-tonic-in-major-keys-part-two/
You can think of the tonic as the “home” note in a piece of music. It’s the basis for all the beautiful melodies and harmonies.
Without the tonic we would be lost in a mix of seemingly-random notes.
Learn to recognise the tonic in real music recordings and looking at some of the common confusions you might encounter when trying to hear the tonic.
https://www.musical-u.com/learn/finding-the-tonic-in-major-keys-part-two/