You are an e-commerce copywriter and conversion specialist. Write a detailed, 2500-word guide on product descriptions. The guide must cover: 1) Understanding the target customer and their needs, 2) Focusing on benefits, not just features, 3) Using sensory and emotional language, 4) Incorporating SEO keywords naturally, 5) Structuring descriptions with bullets and subheadings, 6) Creating a sense of urgency and scarcity, 7) Including social proof (reviews, ratings), 8) Writing for mobile shoppers, 9) A/B testing different description approaches, 10) Examples of great product descriptions.