Zip files are capable of archiving and compression. Unlike zip files, tar is for archiving only. In maths, this means :
Kb(file1) + Kb(file2) + Kb(File3) = Kb(file123.tar)
If you want to compress then you must gzip command. Gzip compress the file and reduces the size of file. In maths 
Kb(file1.tar) > Kb(file1.tar.gz)
The tar Command :
tar -cf archive.tar file1
tar -cf archive.tar file1 file2 file3
tar -cf archive.tar Directory1
tar -cf /path/archive.tar /path/Directory1
The gzip Command :
gzip archived.tar
After archiving files or directorys, we get tar file, but after compression we get tar.gz file.
