Slow-reacting, virgin guy that girls keep in their hip pocket as guy friends to test out their social experiments, as the girl prepares to sew their oats with other non-cherry boy guys. Girls have a good personal relationship with their cherry boys and are quite protective of them, never setting them up with other girls, yet never getting romantically involved. Yet sometimes there is sexual experimentation if she allows it. But its only for practice or to gain experience.
Basically the Cherry Boys are the lower rung/first step of the Ladder in a woman's achievements.
"Why don't you go to the prom with Martin, you two are always together?"
"Oh we're just friends. I never thought of him that way. I have my sights on Jim."