An application note is usually a paper to present an application of a specific product. Application notes are usually provided by vendors and manufacturers.
A white paper is a paper describing almost all the things regarding a technology, a concept, or a product. If you read a white paper, then, you will get some overview on the topic.
Application note is a note of applicatin ON a particular product/technology...
White paper (Technical paper) is "A Particular product/technology" The whole description... like the way we used to write papers in college competitions...