What is the difference between dreams and visions?
The words are used interchangeably, especially in Hebrew scripture, and they are often joined together as a single unit—"dreams and visions." It's possible to say that dreams occur to us when we're sleeping and visions occur when we're awake, but scripture also refers several times to "visions of the night."
Speaking personally, I think dreams do indeed come to us when we sleep, and they are very often expressed in symbols. Visions, on the other hand, come to us while we're awake and are much more direct. Dream interpretation is often helpful, but no one has to interpret a vision—it's clear and direct, a new perspective on a current situation.