This document describes TSconfig: A TypoScript-like syntax for configuring details of the TYPO3 backend.
In addition, you can find a quick reference guide to TypoScript templates in TypoScript in 45 Minutes, a complete reference of all object types and properties of TypoScript in TypoScript Reference and explanations of TypoScript syntax in the chapter "TypoScript Syntax" of TYPO3 Explained.