To understand sexuality in ancient Athens it's necessary to remember that the Athenian culture had no corollary to many of the ideas at the root of modern Western attitudes towards sex. Athens had no Eve, shamed by her nakedness, no commandments carved in stone.
What they did have carved in stone were phalluses. Lots and lots of them, by some accounts. Male sexual organs were frequently included in art, literature, drama and even the streets of Athens. Stone pillars called herms, featuring a bust of the god Hermes at their top and an erect phallus at their base, were placed outside houses for good luck.
Nudity was, if not exactly commonplace, perfectly acceptable. Athletic competitions and many artistic representations of the human form were undertaken nude.
Sex was an act defined by the phallus. It was not an act done with a partner, but rather to a partner. The active party penetrated the passive; in all but the rarest case the active party was an adult male citizen. The division of rights, responsibilities and roles in sexual relationships was not simply split along gender lines, but also lines of class, and of age.
The Athenian Wife and the Oikos
Marriage was a contract between two men, the bride's father and her groom. Although most Athenian women were married in their in their mid-teens it was usual for the groom to be a man in his thirties.
A wife's primary purpose was the production of legitimate heirs. To claim citizenship under the laws of Pericles, an Athenian had to prove both parents were astoi. For a man being astos meant he was a citizen, but for a women being astos simply meant she transmitted citizenship to her sons, and that her daughters could be breeders of citizens.
Athenian wives spent much of their time within the home, overseeing the household or oikos. They were expected to be escorted when they left the home, as the only way for a man to guarantee that his wife's children were his was to keep an eye on her. Aristocratic women, wives of citizens, did not play a significant role in the external affairs of the city or polis with the notable exception of their participation in public funerary rites. In fact, the tensions between oikos and polis were a frequent subject in Greek tragic theater, such as the plays Lysistreta and Medea
Adultery was treated as a serious crime, since it called into question the legitimacy of the husband's children. A wife caught committing adultery could be summarily divorced, but her male conspirator could be subject to much more serious punishment, including death.
Even without the occurrence of adultery a man could divorce his wife simply by rejecting her in front of witnesses or sending her back to her family home. Before a woman had her first child her father could also end the marriage and bring her back to his household or marry her to another man of his choosing. It was possible for a woman to initiate a divorce, but only if she could find an archon (Athenian official) willing to accept her reasons for requesting the divorce be granted. With most of her time spent in her own home, and her husband able to confine her there entirely if he chose, a woman's chances of successfully petitioning for divorce were slim.
Prostitutes, Concubines and Courtesans
With the citizens' wives cloistered in their own homes for most of their lives, the state felt they had a duty to ensure availability of sexual partners. Prostitution not only had no social stigma associated with it, it was totally legal and even taxed. Many of the brothels in Athens were owned by the state, although some were private enterprises.
Athenian society had five different types of prostitutes: slaves in the brothels, streetwalkers or pornai (from whom we get the word "pornography"), symposia call girls called heteras who often danced and played musical instruments, concubines and courtesans.
Prostitutes in brothels and on the street had a fairly miserable existence, the rate they could charge was limited by law, and women in brothels were often expected to spend time between clients weaving or engaged in other crafts to further generate income for the brothel. Concubines generally entered into longer-term arrangements with a single man, and enjoyed better pay and an overall higher standard of living than street and brothel prostitutes.
The courtesans were educated women, sought after for more than just sexual intercourse, they were skilled conversationalists and the most worldly of Athenian women. Although the social freedoms enjoyed by a courtesan were limited by contrast with many other contemporary cultures, they were greater than those enjoyed by any other group of Athenian women.
Homosexuality in Athens
The Lover and Beloved
If people know one thing about ancient Greek sexuality, it's usually that there was no shame associated with homosexuality. Because the Athenian notion of sex was that of penetrator and penetrated, there wasn't the conceptual distinction between male-female and male-male relationships prevalent in modern Western society. In the Platonic dialogue Symposia a legend is discussed which details the origins of humankind as two-headed creatures, existing in male-male, female-female and male-female arrangements. Separated by the gods, each half is destined to seek its match.
Athenian citizens were socially encouraged to pursue younger male lovers, boys who had entered puberty. These men would likely themselves have been the other half of such a coupling in their younger years, their role shifting to the active penetrator as they aged. In such pairings the older man was called the erastes (the lover) and the younger was called the eromenos (the beloved). Although sexual intercourse could occur it wasn't always physical culmination of these pairings.
The erastes was expected to serve as an educator, role model and protector for the eromenos, who in turn rewarded the older man with his youth and beauty. Traditionally the erastes was expected to court the eromenos, to demonstrate the sincerity of his interest in a relationship that surpassed the merely sexual. Likewise, the eromenos was expected to withhold capitulation for long enough to ensure the older man would be an appropriate mentor.
Sappho, a poet and teacher from the Isle of Lesbos, is famously known for her love poetry to girls and women, and for her female-female relationships. Although there is ample evidence of lesbian relationships throughout ancient Greek history, it seems likely that with the rigid constraints on Athenian wives leaving their homes the opportunity for lesbian relationships was limited to women of the household.