extract : to untar (extract) a file named   filename.tar   type:

[ tar xf filename.tar ]

or this will list the files as they are un archived:
[ tar xvf filename.tar ]

or lets say you have (a huge) archive.tar and you only want the directory named   foo   extracted out of it,try this:

[ tar xf archive.tar foo ]   (this also works for just one file. it will show up with the position in the original directory structure)

to list the files in a tar archive named   filename.tar   type:

[ tar tf filename.tar ]

if the archive is huge you may want to send the output to a file and then look at it:

[ tar tf filename.tar > a_file ]

the dash before the tf was not needed on my system which is RedHat with kernel version 2.4.18-14.

create an archive: [ tar -cf ]
to make the directory stuff a tar archive called stuff.tar type this after you have moved out of the stuff directory:
[ tar -cf stuff.tar stuff ]