LFS 7.4 - 5.6 Linux 3.10.10 API Headers (video 12)
The file "linux-3.10.10.tar.xz" can be uncompressed and unarchived (extracted) using the command "tar xvJf linux-3.10.10.tar.xz".
"UPPERCASE J"
The "x" - means, extract files from an archive.
The "v" - means, verbosely list files processed (show the activity).
The (uppercase) "J" - means, extract a .xz file.
The "f" - means, use the file I am specifing.
You can look this stuff up by opening terminal and entering "man tar" and or google it