Answer to Question 1
As sand is dropped in front of the migrating dune on the slip face, it forms layers at an angle in the prevailing wind direction. Over time and dune migration, these layers pile up, but their defined inclination remains and is called cross bedding. This sedimentary structure is a unique characteristic that can be used to tell the geologic story from the rock record.
Answer to Question 2
Loess is wind-blown silt carried in suspension that forms extensive blankets when deposited. Sand dunes are ridges and mounds of sand formed by wind. Silt is typically carried much farther distances than sand.