Gay man

A gay man is a homosexual man. This means a man who is sexually attracted to other men, and not to women.
Gay rights movement.
Gay men were involved in the early gay liberation (a movement of homosexuals who want to be treated equally to heterosexuals) movement. Gay liberation is the political and social movements that promote LGBT equality and rights. However, there was conflict between homosexuals and transgender people in the gay right's movement. In the 1970s some homosexual activists wanted the transgender people out of the gay's rights movement. They wanted gay liberation to be accepted by society. They believed transgender people were less accepted by society and might hurt the gay movement.
Gay men as parents.
Many gay couples want to have children of their own. In order to raise children, they sometimes adopt. However some places do not allow homosexual couples to adopt children, so many of them want to be able to adopt children.
Some gay couples also have their own biological children. To do this they may use surrogates. This is when sperm from one father is placed in a female surrogate to make a pregnancy. Some gay men do this with a friend they choose to be the donor. However many may use professional surrogate agencies. These are medical businesses that match couples who need surrogates with women who will carry the child until birth.
Law and religion.
Unlike lesbian sex between females, gay sex is against the law in many places. Some religions that say nothing about gay female sex condemn gay sex between men. Abrahamic religions usually see all homosexual relations as immoral. 
In most parts of the world gay couples cannot marry. This means they do not have the legal benefits and protection of marriage. This can cause gay men, and lesbians, many problems.