Having sex in a dream needs no further interpretation. It is what the dreamer wants it to be. The human mind is amazing in that it allows us to fantasize and visualize our desires in dreams as if it was real.
Dreaming of sex is often the result from and onset of falling in love, physical attractions, and longing for someone.
If you are feeling a lack of intimacy or connection in your waking life, a dream about having sex may be a way for your unconscious mind to compensate for this. The dream may be a way for you to feel closer to someone, even if it is only in your dreams.
If you are feeling curious or adventurous in your waking life, a dream about having sex may be a way for your unconscious mind to explore these feelings. The dream may be a way for you to try out new things and experiment with different aspects of your sexuality.