The Nikko ND-500 is a 500-denier waterproof and breathable fabric used as a material for outdoor gear like tents, backpacks, and jackets. It is designed to protect against heavy rain and wind while allowing for adequate breathability, helping to prevent sweating and discomfort during strenuous activities. The fabric is durable and can withstand prolonged exposure to the elements, making it a popular choice for outdoor enthusiasts in demanding environments.