Not infrequently the Lord makes his mind and will known to his people by dreams. “All inspired dreams are visions [see 1 Nephi 8:2], but all visions are not dreams.
Visions are received in hours of wakefulness or of sleep and in some cases when the recipient has passed into a trance; it is only when the vision occurs during sleep that it is termed a dream.” (Mormon Doctrine, p. 208.)
When one is freed from the distractions and vicissitudes of life in sleep, then the message or impressions of an inspired dream often distil upon the soul of the recipient in an equally powerful way as a vision in the waking state. (For examples see Genesis 15, 20, 28, 31, 37, 40, 41; Judges 7; 1 Kings 3; Daniel 2; Matthew 1, 2, 27.)