The A9 algorithm is the search ranking algorithm used by Amazon to determine the placement of products in search results. It prioritizes relevance to the customer's search query, customer satisfaction, and likelihood of purchase. Factors influencing the A9 algorithm include detailed and keyword-optimized product titles, high-quality images, competitive pricing, positive customer reviews, and effective inventory management. Unlike traditional search engines that focus on a broad array of SEO factors, the A9 algorithm is finely tuned to maximize sales by closely aligning with customer intent and product relevance on the Amazon platform.