The song describes a relationship between an older man and a 17-year old girl. In the first verse, he tries to convince her to sleep with him despite knowing their relationship is wrong. Over time, the casual relationship becomes more serious as they start living together, causing him to realize she is too young for him. Throughout the song, he repeats the refrain "they're just girls" to remind himself not to get too attached, as she is still a teenager, while their growing involvement leads to arguments as he tells her they cannot continue and she should be with someone her own age.