Typically more traditional, capital intensive companies use customer financing for a portion of their startup capital.
For instance, suppose I invent a new type of transformer with some benefit or the other. I approach the power companies with my prototype and explain that I need capital to produce it, so if they pre-order, I'll offer them discounts and other benefits.
This helps me approaching the banks and investors too, if I can get firm orders out of the power companies, because it demonstrates a market interest in my product.
What kickstarter has done is made it possible for this sort of arrangement to work with the public, pre-buying new consumer goods.
But to answer your question, what the customer gets is 1) a product that they want, which otherwise wouldn't be available, 2) in exchange for their risk that the product won't be delivered, they get various incentives, typically discounts.
For instance, suppose I invent a new type of transformer with some benefit or the other. I approach the power companies with my prototype and explain that I need capital to produce it, so if they pre-order, I'll offer them discounts and other benefits.
This helps me approaching the banks and investors too, if I can get firm orders out of the power companies, because it demonstrates a market interest in my product.
What kickstarter has done is made it possible for this sort of arrangement to work with the public, pre-buying new consumer goods.
But to answer your question, what the customer gets is 1) a product that they want, which otherwise wouldn't be available, 2) in exchange for their risk that the product won't be delivered, they get various incentives, typically discounts.