vxVistA Open Source software is derived from the VistA software developed by the US Veterans' Administration and released under the Freedom Of Information Act, or FOIA. That version of VistA is called "FOIA" VistA. Because of the simliarity between FOIA VistA and vxVistA, many documents published by the VA are good starting points for understanding vxVistA. The following list links to some VA documents.
The VistA Monograph provides an overview of the whole VistA system. Not every package described in the Mongraph is available as part of vxVistA.