The software development lifecycle is a cycle that includes planning, testing, and deploying of software. It has six phases: collection of requirements and analysis, design, implementation, testing, deployment, and maintenance. The first phase involves gathering information about the software's users, usage, and requirements, which is then analyzed to validate the data. The design phase creates a system architecture and describes hardware requirements. Implementation involves coding and dividing work into modules, while testing checks the code against requirements. Deployment delivers the software to customers, and maintenance solves problems that arise during use.