What is the function and meaning of dreaming?

sometimes when i dream, i dream short and blurry dreams. but i seem to know what is going on in that short dream because i see some of it. Get it? if you dont i mean i see dreams but dont understand them. Way later on I feel Deja Vu. And a scene happens that i saw in my dream. It is freaky weird but true. If you want to hear more of this story email me at strawberry0923@gmail.com