means they are sexually or romantically attracted exclusively to people of one's own sex or gender (used especially of a man).
"the city's gay and lesbian people"
If a man/boy likes another man/boy in a romantic way then they are gay.
Billy is gay. Billy tried to kiss Aaron. Aaron is not gay. Aaron likes Nikira.
Two boys lay in bed and sleep together have a nice day without any girls.They start to date and marry and adopt a baby.
Jeff: Hi I am gay
Harry: What? you lay in bed?
Jeff: Yeah whats the matter?