Lesbian is the word used to describe women, fem-aligned, or non-binary people who are attracted to women or fem-aligned people. One might come across the terms "Sapphic" and "WLW" while researching lesbianism. Lesbians are often classified between "butch" or masculine lesbians or "femme" or feminine lesbians - however, not everyone fits on this spectrum.
Lesbian is usually used to describe gay women or fem-aligned people, but it is possible to be non-binary and lesbian. The white stripe in the lesbian flag is often used to represent trans women, GNC, and non-binary lesbians.
The word originally referred to inhabitants of the island of Lesbos, until the 19th century where it took on the meaning of "female homosexuality", due to numerous writers using it in reference to Sappho.
The poet Sappho (c. 610–c. 580 BCE) lived on the island of Lesbos. Although historically her attraction to women has been erased, she's known today for her poetry featuring passionate descriptions of love for women and has thus been seen as a symbol of female homosexuality.
When looking for the lesbian flag, one may come across a purple flag with a black triangle and a labrys (a double headed axe), drawn by graphic designer Sean Campbell in 1999.
This flag does not represent the Nazis.
The black triangle was put there to commemorate the sisters we lost during the holocaust and who were forced to wear a black triangle in concentration camps. The colour purple was associated with the poet Sappho based on her writings ; the axe is a labrys which is associated with the Amazons (a mythological group made entirely out of female warriors) and was a symbol used by the lesbian feminist community in the 70s and 80s.
There's also one with a gradient of pink. The pink one used to be the lipstick lesbian flag, before being adopted as the general lesbian flag, and was first seen in the weblog This Lesbian Life in 2010. The flag is for lipstick lesbians with the stripes having little meaning other than being stereotypical feminine colours.
Another flag is the orange gradient one. It's used by butch lesbians and was designed by Tumblr user butchspace in 2017.
The most recent flag is the sunset flag, designed by Tumblr user Emily Gwen in 2018. It combines the colors of the lipstick and butch flags into one single flag.
It is not possible to become or chose to be a lesbian, homosexuality is innate. However, some people may come out and discover themselves only later in life, due to external factors such as education, societal norms, religion etc.