TYPO3 Explained 

API A-Z 

This chapter describes the core functionality of TYPO3 including API and framework configuration.

Administrations 

Including Installations, Upgrades and updates, Troubleshooting for administrators, and Backend User Management

Configuration 

Including System configuration and the global settings.php, TypoScript, the Configuration module, and Feature toggle API

Coding guidelines 

This chapter contains a description of the formal requirements or standards regarding coding that you should adhere to when you develop TYPO3 extensions or Core parts.

Extension development 

Learn how to write site packages and other custom extension with or without Extbase.

Security guidelines 

This chapter describes some typical risks and advises how to protect a TYPO3 site in order to ensure it is and stays secure and stable.

Automated testing 

This chapter goes into details about automatic testing: Writing, maintaining and running them in various scopes.