complex carbs are polysaccharides and simple carbs are mono- and disaccharides
I don't really know what exactly this is supposed to mean either - but generally you can divide the complex carbs into starchy (brown rice, fullwheat bread, oatmeal etc.) and fibrous (veggies!) ones. simple carbs are sugars and the like. go for complex carbs all the way.
I'd suggest you have rather fibrous carbs at night with some good protein.