The Network Media Library plugin for WordPress Multisite provides a central media library shared across all sites in the network. It achieves this by designating one site as the central media library and temporarily switching the context to that site during media operations (upload, insertion, editing, etc.). The plugin hooks into numerous WordPress actions and filters to intercept media-related requests and redirect them to the central site. It also includes compatibility layers for popular third-party plugins like Advanced Custom Fields and MultilingualPress to ensure they work correctly with the shared media library. The code is organized into a single main file with several classes encapsulating specific functionalities, such as managing context switches, preserving post thumbnail IDs during save operations, and handling ACF field rendering.