What does this SQLCMD statement do?
Sure it is saying to use SQLCMD.EXE connecting to the server instance VMLIVE-DATA\SQLSERVER, to run the script that will restore the GIS_ENG from a backup of the DB_ENG database, replacing the existing GIS_ENG if there is one.

The bulk of the text is the script -Q"RESTORE  ...  STATS=10".

The SQLCMD and RESTORE DATABASE parameters are define in the SQL Server documentation.

SQLCMD.EXE - http://technet.microsoft.com/en-us/library/ms162773.aspx

RESTORE DATABASE - http://technet.microsoft.com/en-us/library/ms186858.aspx

By default SQLCMD uses Trusted Connections (describe in the SQLCMD link) so it requires this to be run by a login with rights to restore a database.