The .sxw file is a .JAR file (which is basically the same as a .ZIP file).
The manifest.xml file is the difference between .ZIP and .JAR,
apparently. It makes searching the files easier, and the documentation
claims that this file is uncompressed, so that it can be easily
read. I have not tested this, but it seems like a good idea.
content.xml - the text of the document
styles.xml - the styles used by the document
meta.xml - various meta-information (author, etc)
settings.xml - the Word Processor settings used.
META-INF/manifest.xml - a list of all these files, plus any others used in the document