As a user you need not really be concerned with how the reporting system works, that is, you don't need to worry about how an invoice, drug label, stock list, etc is generated, only how to ask for it.
It is worth noting that when printing things, it is normally possible to preview the document before actually printing it, and also to email the document without printing it. When running reports, it is also possible to 'export' the data in CSV format so that it can be used in spreadsheet and other programs. See also Concepts|Printing.
All printing in OpenVPMS is customisable. If you don't like the way the invoices look, this can be changed. Similarly, if you need a report listing all dogs by name, it is possible to make this.
Skip the remainder unless you are an administrator or want to know "what's under the hood".
All documents and reports are controlled by 'Document Templates' which specify how and what to do to generate the document or report. Two facilities are used to form up the content: JasperReports and OpenOffice.
OpenOffice is used for simple documents (like patient certificates). You use an OpenOffice document template to specify the document content. Since OpenOffice can also handle Microsoft Word documents, you can also use these. They are held in files with the extension .odt (or for Word, .doc). Anyone with normal word processing skills should be able to create and modify these templates. Note that OpenOffice cannot handle the default .docx format used by Word 2007 and beyond. If you are using Word, you need save documents to be used by OpenVPMS/OpenOffce in .doc (ie Word 97-2003) format.
JasperReports is used for more complex documents such as invoices, statements, reports etc as these typically have multiple rows of data and require groupings and other data processing functions not available in OpenOffice. The iReports program is used to design, test and maintain these reports. They are held in files with the extension .jrxml. Using iReports requires a reasonable skill level, but anyone with some programming experience should have no trouble. As always, it is easier to proceed by cloning an existing report than building one from scratch.
If you do need to create and modify reports and documents, see Reference|Reports and Forms.