The roughest interpretation of such a dream image relates one's need to have his/her basic needs fulfilled, therefore to have sex. On the other hand, dreams about sexual intercourse may be a metaphor of the harmony and union between one's feminine and masculine aspects of the self.
The sexual act represents the union of the masculine and feminine, the yin and yang, the harmony of the opposites, the animus and anima of human psyche. Animus and anima are concepts of C. G. Jung's theory on human psyche - he stated that anima stands for the feminine inner personality and all feminine attributes present in a male's subconscious. The animus represents the masculine inner personality and all masculine attributes present in a woman's subconscious. According to the famous psychologist and psychiatrist, all men bear a feminine aspect in their psyche and all women have masculine attributes buried in their subconscious.
Consequently, to have sexual intercourse does not only stand for one's primitive needs. It also represents, depending on the case, the fact that a woman has accepted and integrated the animus in her personality or a man has done the same thing with the anima in his psyche. The sexual act denotes the union and balance of masculine (yang) and feminine (yin) energy within one's personality.
Also, we should not forget about the fact that usually the masculine stands for the rational, while the feminine stands for the sensitivity and spiritual side of an individual. As a consequence of this, such a dream image may be considered a metaphor for the harmonious blending of the rational and the spiritual, of reason and emotions, of 'sense and sensibility'.
Accordingly, having sex with someone of the same gender, even though you are heterosexual in the waking life, may not mean that you have gay tendencies, but stands for the acceptance of a certain aspect of your personality or for the masculine or feminine side of yourself, depending on the case.
Dreams in which you makes love to a person you like usually bear a positive significance and stand for bonding, affection, harmony, joy and happiness. Such dreams in which you make love, not simply have sex with someone, are most of the times reflective of your own feelings or of situations in the waking life - you may feel the need to receive affection and have someone to share good and bad times with, you may love someone in the waking life whom you want to conquest or with whom you already have a relationship with etc. On the other hand, pleasant dreams like this may be brought about by a state of emotional balance and general equilibrium you have achieved in your waking life.
To dream that you make love to someone you are attracted to is usually a good dream omen which may foretell meeting an agreeable and nice person in the waking life. When premonitory, making love dreams may also announce success, prosperity and accomplishments in real life.
If in your dream you are longing to make love to someone and you are just about to do it, but you wake up before the act takes place, this stands most of the times for your insecurity and doubts when it comes to your ability to conquer someone. Such dreams are usually brought about by a low-self esteem and the lack of confidence in yourself. You may have a complex about the way you look, you may feel unattractive and/or unable to have a durable love relationship etc.
But dreams of having sex or making love may also be compensatory dreams and represent a form of wish fulfillment. If one is unsteady and finds it hard to get involved in a long, constant relationship or if one longs for such a relationship but he hasn't found the right person yet, he may have such dreams to compensate for what he does not have in the waking life.