There a mainly four different types of dreams. The first are the literal dreams which has little underlying significance; it is simply an emotion or feeling both physical, emotional, mental, or spiritually that get stuck in your unconscious mind and are being replayed over and over again. (PAST)
Then their is prophetic dream which is where you dream of near or distant possible events in the future. These can be changed often if they seem insignificant, but mot of the time they are dramatic events that take more effort to change. ( like when I was young I dreamed that a vulture ramming into two towering obelisks ) FUTURE
The third is a repetitive dream which repeats itself over and over again, usually attempting to make a point or warn you of something positive or negative. Can be either a literal dream or a prophetic dream. (PAST - FUTURE)
The fourth is a symbolic dream which expresses a deep meaning through symbolism and metaphors that you yourself are use to.
You can induce dreams either through a meditation state, through the use of dream pillows with herbs and crystals. The average person experiences these types of dreams multiple times a night but we completely forget about them when we wake up in the morning, not even realizing we had them. That is why its good to have a journal or some kind of way of remembering the dreams.
Dreams can be dangerous they are a form of stimulant for the unconscious mind. And sence the unconscious mind and the conscious mind are connected together. So if you feel like your being attacked in one you feel like your being attacked in the other. For protection you could use a dream catcher with your power or spirit animal in the center to fight off and consume the bad dreams.
Hope this helps