It usually does not mean anything when a person talks while sleeping. Talking while asleep is usually only a problem when signs of fear accompany the sleep-talking.
Talking while asleep is sometimes a sign of stress, or of having drunk too many caffeinated beverages. When stressed, it can be a sign of an overworked mind trying to work through the day's problems. Sleep-talking can also be a normal side effect of some medications. The time to worry about sleep-talking is when fear-related acting out or potentially dangerous sleep-walking accompany the sleep-talking. Sleep terrors and REM sleep behavior disorder can leave the person screaming, thrashing around, or even hitting and kicking anyone nearby. In these cases, medical attention is advised, because the person can get hurt or hurt someone else.