launchd
launchd is a system service management framework for macOS that handles the launching, supervision, and termination of daemons, applications, processes, and scripts. It serves as a unified replacement for traditional Unix init systems and cron, providing a centralized way to manage system and user-level services through property list (plist) configuration files. It is integral to macOS startup, login, and background task automation.
Developers should learn launchd when building macOS applications or system tools that require automated execution, such as scheduled tasks, background services, or login items. It is essential for creating daemons that run persistently, agents that launch on user login, or timed jobs that replace cron, ensuring proper integration with macOS security and system management features like sandboxing and energy efficiency.