You need to read the manual pages for the tar cmd; use this at the cmd line
man tar
anyway,
tar - tape archive cmd
x - extract content
v - verbose
f - next arg is file to work on
z - file is compressed with gzip; see gzip man page
-C - next option is a target dir
/opt - target dir to put extracted content into
bookmark/read this:
http://rute.2038bug.com/index.html.gz