What is SDLC and what are its main phases?

SDLC (Software Development Life Cycle) is a systematic process for planning, creating, testing, and deploying software. Main phases: Planning (scope, feasibility), Requirements Analysis (gather and document needs), Design (architecture, system design), Development (coding), Testing (verify functionality), Deployment (release to production), Maintenance (updates, bug fixes). Different methodologies (Waterfall, Agile) implement these phases differently.