Charts work in the same way as the <Value/> component - you can add them anywhere in your markdown and reference SQL queries on the page.
So let's try to answer the question the Needful Things owner had about sales.
The first chart shows sales have overall been increasing across the three year period (though not every month).
The second and third charts show this is mainly due to an increasing number of orders - the average basket size has been relatively consistent over the period.
Check out the Components section to see the full list of available components.