What does Deuteronomy 24:3 mean?

her first husband can’t marry her again after she’s been with another man. That would be offensive to God. Don’t bring that kind of guilt into the land God is giving you. Deuteronomy 24:3 - Modern Text Bible

(This rule is about respecting the seriousness of marriage and divorce. It’s meant to prevent treating marriage lightly or as something to be reversed at will.)