A Backend Developer designs and maintains server-side applications and databases, crucial for business functionality and user experience. Responsibilities include API development, database management, and optimizing application performance. Essential skills include proficiency in server-side languages (e.g., Python, Java), database knowledge (SQL, NoSQL), and familiarity with version control. Typically working in an agile environment, they collaborate with frontend developers, UX/UI designers, and product managers. Career advancement may lead to roles like Lead Developer, Tech Architect, or CTO, with opportunities in diverse industries.