Audit: Critical audit matters vs. Key audit matters

Hi i need some clarification:

For critical audit matters is this required by public companies and are only for public companies? and where are they included in the audit report? at the end? or where the explanatory paragraphs go?

For key audit matters, is this only for private companies? and are they required by AICPA? where does this paragraph go in the explanatory paragraph section?

thank you !!!!!!!!