CMS
CMS is the abbreviation for Content Management System, a software program for managing, operating, and displaying a website. It is a web-based (browser-based) system that does not require any software to be installed on the workstation.
Content element
Content elements contain corresponding content and a unique ID (uid). Each content element is part of a page to be displayed in the frontend.
Content type
A content type describes a content element in TYPO3 and can be, among other things, text, an image, or a file.
TYPO3-Extension
A TYPO3 extension (or “add-on”) is a module with special functionality that can be integrated into the TYPO3 base system via defined interfaces.