When you look at waterproofing technologies there are two distinct options.
The first is a chemical coating which closes pores in fabric and limits the breathability. This is the most common waterproofing technology used in most garments.
STORMTECH'S H2XTREME uses a highly breathable and waterproof membrane technology. This membrane has microscopic holes in the fabric that work to let moisture vapour escape while keeping water and wind out.