This refers to God's rule as king. The phrase "kingdom of heaven" is used only in the book of Matthew. If possible, use "heaven" in your translation. (See: [[rc://en/ta/man/translate/figs-metonymy]])
# bind on earth shall be bound in heaven ... loose on earth shall be loosed in heaven
This metaphor means that God in heaven will approve of what Peter allows or forbids on earth. (See: [[rc://en/ta/man/translate/figs-metaphor]])