It means becoming physically intimate with each other as one flesh.Marriage involves three elements, commitment, care and concern, and emotion.Each of these three relationships have two common characteristics, a commitment to the responsibilities of that particular kind of relationship and a genuine care and concern for the other person in a particular kind of relationship.Friendship and marriage have a third characteristic - affection and attraction, although the nature of the affection and attraction is different.
Prov.17: 17 says, “A friend loves at all times.” Prov.18: 24 says, “There is a friend that sticks closer than a brother.” Prov.27: 6 says, “When a friend rebukes you, that rebuke can be trusted.” Prov.27: 9 says, “The pleasantness of having a friend springs from his earnest counsel.” Prov.27: 10 says, “Do not forsake your friend.” These verses bring out the fact that the Lord blesses friendship and encourages us to develop them.
It also involves the joy of romantic desire/attraction and intimacy and sexual desire/attraction and intimacy.
The Song of Songs, the dialogue between King Solomon and his bride, is a celebration of the romantic and physical love between a husband and wife.
Of these three relationships, the Scriptures only speak of romantic attraction and desire being expressed in marriage.
Song of Songs gives a beautiful picture of the feelings and expression of romantic desire and attraction.