What does Matthew 3:11 mean?

I’m baptizing you with water to show you’ve changed, but someone is coming after me who’s way more important than I am. I’m not even worthy to carry his sandals. He’ll baptize you with the Holy Spirit and with fire. Matthew 3:11 - Modern Text Bible

(John says his baptism is just the beginning; the one coming after him (Jesus) will bring a much deeper transformation.)