Sappho was a poet from the island of Lesbos who lived between 630 and 612 BCE. She wrote many love poems addressed to women and girls. The love in these poems is sometimes requited, sometimes not.
Sappho is thought to have written close to 12,000 lines of poetry on her love for other women. Of these poems, only about 600 lines have survived. As a result of her fame in antiquity, she and her native island have become emblematic of love between women.
The term Sapphic love, therefore, has become synonymous with lesbian love.
On a related note, the great philosopher Plato mentions lesbianism in his Symposium; he discusses women who “do not care for men, but have female attachments.”