The legacy wiki pages are here for reference purposes only.
For up-to-date information make sure to check the documentation section.

The content section is where the editors author content. The content tree is the backbone where you can navigate the hierarchical content and through the context menu (right click on a tree node) can perform certain actions depending on assigned rights.

Read more about: is the community mothership for Umbraco, the open source cms. With a friendly forum for all your questions, a comprehensive documentation and a ton of packages from the community. This site is running Umbraco version 7.5.2