What does it mean when your sleeping and you hear your boyfriend's voice in the garage talking to his friend?

The simplest explanation would be that the dreamer's boyfriend was in the garage, talking with someone else while the dreamer was asleep. Sounds from other rooms or from outside often affect a sleeper's dreams. Otherwise, if the dreamer thinks about the boyfriend a lot, it would not be surprising to dream of him. A conversation in the garage would not have any special significance in a dream.