Homosexuality is a disease? Homosexuality is sin? These issues have been very controversial, although American Psychiatric Association and the National Psychological Association has declared that "homosexuality is not a mental illness," but the United States National Institute for Research and Treatment of homosexuality still been working on pathological studies discussed homosexuality. Currently humans or different races around the world still mainly heterosexual, and homosexual and only a minority; thus being labeled gay called "label"; and to mainstream heterosexual society is unable to accommodate homosexual existence. This article by the relevant literature review and organize to explore the definition of homosexuality, causes, determination index, cognitive, religious views on homosexuality, homosexual movement, the rainbow flag and conflicts of modern social aspects. We expect general civilian could have a better understanding and respect of homosexuality.