Yes, the export writes the site content into Sites.xml in your site package, and import imports that file again. See also the help:
$ flow help site:export
Export sites content
./flow site:export [<options>]
--site-node the node name of the site to be exported; if none given
will export all sites
--tidy Whether to export formatted XML
--filename relative path and filename to the XML file to create.
Any resource will be stored in a sub folder "Resources".
--package-key Package to store the XML file in. Any resource will be
stored in a sub folder "Resources".
--node-type-filter Filter the node type of the nodes, allows complex
expressions (e.g. "TYPO3.Neos:Page",
This command exports all or one specific site with all its content into an XML format.
If the package key option is given, the site(s) will be exported to the given package in the default
If the filename option is given, any resources will be exported to files in a folder named "Resources"
alongside the XML file.
If neither the filename nor the package key option are given, the XML will be printed to standard output and
assets will be embedded into the XML in base64 encoded form.
And this is the import:
$ flow help site:import
Import sites content
./flow site:import [<options>]
--package-key Package key specifying the package containing the sites
--filename relative path and filename to the XML file containing
the sites content
This command allows for importing one or more sites or partial content from an XML source. The format must
be identical to that produced by the export command.
If a filename is specified, this command expects the corresponding file to contain the XML structure. The
filename php://stdin can be used to read from standard input.
If a package key is specified, this command expects a Sites.xml file to be located in the private resources
directory of the given package (Resources/Private/Content/Sites.xml).