To create/decompress a tar zip (tar.gz) archive

To create a tar zip (tar.gz) archive:

$ tar -zcvf <archive name>.tar.gz directory_to_compress

To decompress the archive:

(To the current directory)
$ tar -zxvf <archive name>.tar.gz

(To a specified directory)

$ tar -zxvf <archive name>.tar.gz -C /extract_directory/