Dreams are essentially a bunch of random images put together by your subconscious mind. You have around 5000 each night and they pretty much don't mean a damned thing. One exception being that your first dream tends to involve whatever you were thinking about when you fell asleep.
God spoke to people many times throughout the Scriptures in dreams. Examples are Joseph, son of Jacob (Genesis 37:5-10); Joseph, the husband of Mary (Matthew 2:12-22); Solomon (1 Kings 3:5-15); and several others (Daniel 2:1; 7:1; Matthew 27:19). There is also a prophecy of the prophet Joel (Joel 2:28), quoted by the apostle Peter in Acts 2:17, that mentions God using dreams. So the simple answer is, yes, God can and does speak through dreams. However, there is a difference in how we apply that truth today. We must keep in mind that the Bible is finished, having revealed everything we need to know from now until eternity. This is not to say that God does not work miracles or even speak through dreams today, but anything God says, whether it is a dream, vision, impression, or "still small voice," will agree completely with what He has already revealed in His Word. Dreams cannot be put into a place of authority over the Scriptures. (cont in comments)
Dreams have historically been one way God has spoken to man. Jacob dreamed of a ladder, Joseph dreamed of sheaves and stars, he interpreted dreams, and there are many other dreams recorded in the Bible. But today, dreams appear to be regarded as the product of the unconscious, not an encounter of the supernatural with the natural. I do not know if dreams have meaning other than the meaning they have for the dreamer.
I'm not religious but yes dreams are one of the ways that God coveys his messages to man, there are several instances in the bible from the old testament to the new testament that God has spoken to man. If we were to pull out the subject about dreams in the bible there wouldn't be much left.========read===========For God speaketh once, yea twice, yet man perceiveth it not. In a dream, in a vision of the night, when deep sleep falleth upon men, in slumberings upon the bed; Then he openeth the ears of men, and sealeth their instruction, (Job 33:14-16 KJV)=======read========And it shall come to pass afterward, that I will pour out my spirit upon all flesh; and your sons and your daughters shall prophesy, your old men shall dream dreams, your young men shall see visions: (Joel 2:28 KJV)
Dreams do have meaning. Yes, some of them are random, but that doesn't matter - consider the things you see in your dream such as colors, people, shapes, symbols, numbers, weather, and the things that just seem to fascinate you. They all have meaning. Thoughts and events that have happen to you through out the day record in your mind. When you sleep, those thoughts carry over to your subconscious mind. As for religion, there are over 5,000 references to dreams in the bible, and every religion takes dreams in a different way.