Behavior-Driven Development (BDD) is an Agile software development practice that focuses on collaboration between developers, testers, and non-technical stakeholders to define how an application should behave from the end user's perspective. BDD aims to reduce misunderstandings by ensuring that all stakeholders have a shared understanding of the system's behavior.

In BDD, user stories are written in plain language (usually in a structured format like Gherkin) to describe desired behaviors and system functionality. These stories are often structured in a "Given-When-Then" format, making them easy to understand by both technical and non-technical team members.

Once these stories are defined, developers write automated tests to validate the expected behavior as they code the application. The goal is to ensure that the software behaves as expected, preventing misalignment between the intended requirements and the delivered product.

BDD fosters better collaboration between teams, improves communication, and ensures that the development process is driven by the end-user's needs, leading to higher-quality, user-focused software.