Well, a guy is a human who identifies as male. When we say "two guys," we mean two male individuals. They could be friends, brothers, or lovers. It's like when you and your friend are both girls or both boys, except it just means there are two boys together. Just like how it's okay for you to be friends with another girl or another boy, it's okay for two guys to be friends or in a relationship together. Love is love, no matter who it's between!