From MEPIS Documentation Wiki
Tar is a good utility to know if you're going to be downloading and compiling software, because most source is distributed as a compressed tar file.
Create a gzip compressed tar file
tar -czf newFileName.tar.gz file1 file2 folder1 etc
Create a bzip2 compressed tar file
tar -cjf newFileName.tar.bz2 file1 file2 folder1 etc
The tar.gz and tar.bz2 extensions are merely conventions, they aren't absolutely necessary. bzip2 provides better compression ratio than gzip, however gzip is faster.
Extract a compressed tar.gz or bzip2 file
tar -xvf filename.tar.gz
tar -xvf filename.tar.bz2