ROOT offers a rich set of code examples that allow you to see ROOT's building blocks "in action", as part of more complex programs. They are separated in two categories: C++ or python scripts and Jupyter notebooks.
The tutorials are available for all major ROOT releases. These are the links for the latest git snapshot. All scripts are available also in the form of a ROOTBook which can be visualized in NBViewer or tried out interactively in SWAN. Just look for these badges: