Goals and funnels reports are extremely useful for marketers. These reports help to evaluate traffic sources and campaigns, to analyze the user flow through the funnel before conversion, to find drop-off points and bottlenecks in the funnel. Google Analytics is tricky when it comes to funnel configuration.
Unlike many other analytics systems Google Analytics processes the goal and funnel data. It means that you cannot build a funnel report on historical data. you need to configure your goals and funnels first and only after this Google Analytics will start collecting data about funnel flow and conversions.