The pink triangle is one of the two big symbols of the LGBT community. The other is the rainbow flag. The pink triangle was first used in Nazi Germany to mark homosexual prisoners. There was also a black triangle that marked anti-social women. Many but not all of these women were lesbians. Jews wore the famous yellow star of David. If a prisoner was both Jewish and gay, he would wear a yellow triangle overlapped by a pink triangle, creating a star of David.
Homosexuality was illegal in Nazi Germany under a law called Paragraph 175, which made it a felony (a "very serious" crime). About 100,000 people were arrested, with about 50,000 sent to prison. Some were sent to mental hospitals. Some were castrated (had their testicles removed). Some homosexual men were also sent to concentration camps, especially Jewish homosexuals. Between 15,000 and 600,000 homosexual men were sent to concentration camps. Most of them died there. We are not sure of the real number. Prisoners who were Jewish and homosexual may not have been counted as homosexual.
Homosexual prisoners were treated worse than other prisoners. Their death rates were higher than other anti-social groups. One story by a gay man who lived in a concentration camp shows how it was. Pierre Seel was sent to the Schirmeck concentration camp. The Nazis said a public execution would happen. A man was brought out. Seel saw that the man was his 18 year old lover. The Nazis took all the clothes of Seel's lover and put a bucket over his head. Then Seel had to watch as the Nazis let German Shepherds (dogs) maul his lover to death.
After World War II, homosexual men were still not treated well in Germany. The law continued. It was used to hurt homosexuals and to put them in prison. Many spent years in prison.
The pink triangle observes the memory of the homosexual people who died in the Holocaust. It is important not to ignore these deaths. The killing of homosexuals both during WWII and after WWII ended is the secret story of the Holocaust. Using the pink triangle symbol puts these victims in the public view. It is in respect for those who died.