Customer Development is a process used by startups and businesses to understand their customers' needs and validate their product ideas. It involves engaging with potential customers through interviews, surveys, and feedback sessions to gather insights about their preferences and pain points. This helps businesses create products that truly meet market demands. The Customer Development framework consists of four key steps: Customer Discovery, Customer Validation, Customer Creation, and Company Building. Each step focuses on learning from customers and iterating on the product or service based on their feedback, ultimately leading to a better fit between the product and the market.