Here's how they describe it.
You will need to include the Open Flash Chart in your HTML, and you also need to provide the data file on the server. The data file is either a text file, or a .php, Perl, Python, Java (or another flavour of dynamic) page.
For a simple chart you would just drop the data.txt file on your website and point the Open Flash Chart to this URL.
But what we really want is dynamic data that is pulled from a database or calculated or something. To do this you need to create the data file when it is requested. To do this we point the Open Flash Chart to a .php page and this PHP page does your calculations and/or database lookups, then outputs the data file.
To make this a bit easier there are PHP, Perl, Python and Java classes to write the data file for you.