TYPO3 v8 has reached its end-of-life March 31st, 2020 and is not maintained by the community anymore. Looking for a stable version? Use the version switch on the top left.
You can order Extended Long Term Support (ELTS) here: TYPO3 ELTS.
TYPO3 CMS has a lot of documentation available on the documentation web site. The documentation is divided into several sections:
Tutorials and Guides section covers documents which provide step-by-step introductions to specific topics.
The Core Documentation is related to the core of TYPO3 CMS and covers the architecture and API in detail. Also listed are extensive references (hence their name) about configurations and APIs.
The Extensions gathers all manuals related to core and public extensions.
This is admittedly a huge mass of documentation and you may feel lost about where to look next. We recommend the following documents for further studies after this tutorial:
If not stated otherwise, we link to the latest versions of the manuals here, which reflect the latest TYPO3 version (see https://get.typo3.org/ for a list of releases).
Use the Version Selector in the manual, to select the correct version.
And last but not least: Ask on Slack for the best resources for your specific task.