# Background  and Principles

Here are described details about the background and the concepts of VFLP which were not covered by [corresponding chapter](https://docs.virtual-flow.org/documentation-vf1/principles-and-theory) of VirtualFlow in general. This concerns the following topics: 

* [The directory structure](https://docs.virtual-flow.org/documentation-vf1/vflp/untitled-2/directory-structure)
* [The input & output databases](https://docs.virtual-flow.org/documentation-vf1/vflp/untitled-2/untitled-1)