Here is a list of all topics with brief descriptions:

[detail level 12]

Actions
Ajax
API
Feed
MediaWiki constants
DifferenceEngine
Dump
ExternalStorage
▼File Repository	This module handles how MediaWiki interacts with filesystems
File abstraction	Represents files in a repository
▼Hooks	Hooks allow custom code to be executed when an event occurs; this module includes all hooks provided by MediaWiki Core; for more information, see https://www.mediawiki.org/wiki/Manual:Hooks
ResourceLoader Hooks
Installer	The Installer helps admins create or upgrade their wiki
JobQueue
Language
▼File backend	File backend is used to interact with file storage systems, such as the local file system, NFS, or cloud storage systems
File journal
Lock management
Cache
Database	This file deals with database interface functions and query specifics/optimisations
Redis
Media	Media handlers and other classes relating to Multimedia support, with the exception of FileRepo and FileBackend, which have their own groups
Pager
Parser
Profiler
▼ResourceLoader	For higher level documentation, see https://www.mediawiki.org/wiki/ResourceLoader/Architecture
ResourceLoader Hooks
Search
Skins
SpecialPage
Users watchlist handling
Upload related
Entry points	These primary scripts live in the root directory
▼Maintenance
Benchmark
Maintenance archives
TermColorer