Short answers, pulled from the story.
The first known appearance of "homosexual" in print is found in an 1868 letter written by Austrian-born novelist Karl-Maria Kertbeny to Karl Heinrich Ulrichs, arguing against a Prussian anti-sodomy law. The psychiatrist Richard von Krafft-Ebing then brought the term into mainstream use in his 1886 book Psychopathia Sexualis.
The American Psychiatric Association removed homosexuality from its Diagnostic and Statistical Manual of Mental Disorders in 1973, stating that it implies no impairment in judgment, stability, reliability, or vocational capabilities. The American Psychological Association adopted the same position in 1975, and the World Health Organization removed homosexuality from its ICD-10 on the 17th of May 1990.
Scientists favor biological causes of sexual orientation, with more evidence for nonsocial, biological factors than social ones, especially for males. Leading hypotheses include prenatal hormone exposure, genetic factors identified through twin and molecular genetics studies, and the maternal immune hypothesis, which proposes that a mother's immune response to male-specific antigens during successive male pregnancies may influence fetal brain development.
The ancient Egyptian pair Khnumhotep and Niankhkhnum, who lived around 2400 BCE, are commonly regarded as the first possible homosexual couple in recorded history. They are depicted in a nose-kissing position, described as the most intimate pose in Egyptian art, and are surrounded by what appear to be their heirs.
Ten countries or jurisdictions, all predominantly Islamic and governed under sharia law, impose the death penalty for homosexuality, including Afghanistan, Iran, Brunei, Mauritania, Saudi Arabia, and several regions in Nigeria and Jubaland. Many other governments in the Middle East and parts of Africa, Asia, the Caribbean, and the South Pacific also criminalize homosexual activity.
Same-sex marriage in the United States expanded from one state in 2004 to all 50 states in 2015, through a combination of state court rulings, state legislation, direct popular votes, and federal court rulings. Canada had legalized same-sex marriage nationally earlier, through the Civil Marriage Act enacted in 2005.