1) To compress files: 
Examples: 
 tar cvf abc.tar a1.ps a2.tex adir/* # compress files to the file abc.tar
 gzip -9 abc.tar /* # create abc.tar.gz file.
 tar cvfz abc.tar.gz a1.ps a2.tex adir/* # directly create abc.tar.gz file 
 zip abc.zip a1.ps a2.tex adir/* # directly create abc.zip file 
 
Note
 that -9 means the slowest compression method (best compression). By 
default, -6 is used. -1 means fastest compression method (less 
compression). The command zip is compatible with PKUNZIP on pc. Thus, 
the file abc.zip can be uncompressed by WinZip. 
2) To uncompress files: 
Examples: 
 tar xvf abc.tar # uncompress abc.tar file
 gunzip abc.tar.gz # after uncompress, get abc.tar
 tar xvfz abc.tar.gz #unzip and utar *.tar.gz file
 unzip abc.zip #unzip .zip file
 
To view the content of the compressed file: 
Examples: 
 tar tvf abc.tar
 tar tvfz abc.tar.gz
 unzip -l abc.zip