It means becoming physically intimate with each other as one flesh.
How much more pleasing is your love than wine, and the fragrance of your perfume than any spice." Only in marriage may a man and woman enjoy expressing their romantic and sexual desires toward each other.
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.
It shows that God desires that they enjoy the blessings of the union He created.
Song of Songs 1:2 says “Let him kiss me with the kisses of his mouth, for your love is more delightful than wine.” Husbands and wives are to rejoice in each other’s love both romantically and sexually.