How do you explain homosexuality from Freudian perspective?

Freud's views on homosexuality are rather complicated. The good thing about them is that he went through with them very objectively, but a lot of his theories have been overruled in the past centuries.

Freud thought that every human in the world is a bisexual. He didn't mean it in the current way it is used, but he tried to imply that every human has some kind of sexual attraction to both sexes. Freud believed in two opposites that are in a dynamic relationship, sexuality being also one of them. When something traumatic happened that changed the norm, which is in this case heterosexuality, your libido and sexual thoughts started to change towards homosexuality.

He also tried to explain on one of his articles that homosexuality could be resulted from one's childhood. He believed that when someone is growing up, he faces different sexual phases in his life. There is one phase in particular, where you are most likely to face different traumas that can affect your growing. During this phase, you will be attracted towards your mother, and treat her in a way that Freud considered to be sexual. Then again you will feel some agony and jealousy against your father, who you'll feel as a threat. Freud thought this was essential for child's sexual development and that if it was altered, it may have tremendous effects on one's development. This was an accurate theory until it was ruled over by Westermarck theory made by Edvard Westermarck.

The reason that Freud's opinions on homosexuality are so popular is mostly because Freud was among the first psychologists who thought that homosexuality wasn't a bad or a sinful thing. Freud wrote a letter to a mother who wanted Freud to treat her son's homosexuality, where he says this about homosexuality:

"Homosexuality is assuredly no advantage, but it is nothing to be ashamed of, no vice, no degradation; it cannot be classified as an illness; we consider it to be a variation of the sexual function, produced by a certain arrest of sexual development"

Freud all in all had revolutionary thoughts on human sexuality and some of them are still accurate towards this day.