The Saxon-B 9.1 package is a collection of tools for processing XML documents.
The main components are:

- An XSLT 2.0 processor, that can be used from the command line, or invoked
  from a Java application by use of the standard JAXP API. Saxon can be
  integrated with Java applications using the JAXP API, which means it is
  possible for a Java application to switch between different XSLT processors
  without changing the application code. As well as conforming closely with the
  XSLT 2.0 specification, Saxon offers a number of powerful extensions.
- An XPath 2.0 processor accessible via an API to Java applications.
- An XQuery 1.0 processor that can be used from the command line, or invoked
  from a Java application by use of an API.
- An XML Schema 1.0 processor. This can be used on its own to validate a schema
  for correctness, or to validate a source document against the definitions in
  a schema. It is also used to support the schema-aware functionality of the
  XSLT and XQuery processors.

So you can use Saxon to process XML by writing XSLT stylesheets, by writing
XQuery queries, by writing Java applications, or by combinations of the
approaches.