Do five precepts protect?

All five precepts are relatively clearly defined except maybe the third precept. There are different types of women that are prohibited, prostitute is not one of the requirement to break the third precept. If, for example, someone likes to visit prostitute, that person does not break the third precept. Do five precepts protect us from falling to lower realms? What is the purpose of practicing five precepts? What protects you from taking rebirth in the realms lower than human? Thanks.