PlaceholderAPI is a Bukkit/Spigot/Paper plugin that provides a unified placeholder system for Minecraft servers. It allows server owners and plugin developers to display dynamic information (e.g., player name, coordinates, plugin stats) using a simple %identifier_params% syntax. The plugin acts as a central registry for placeholder expansions, which can be loaded from a local 'expansions' folder or downloaded from the eCloud (a remote expansion repository). The architecture is a standard Bukkit plugin with a command router, expansion managers (local and cloud), a high-performance character-based replacer, and an abstract scheduler layer that supports Bukkit, Paper, and Folia. Key entry points include the PlaceholderAPI static API class, the PlaceholderAPIPlugin main class, and the /papi command. External dependencies include bStats for metrics, Adventure for modern chat components, and the Spigot/Paper API. The codebase is well-structured, with clear separation of concerns, extensive use of interfaces and dependency injection, and includes unit tests and JMH benchmarks for the replacer.