Tar file can come compressed or uncompressed. Generally that are compressed using gzip or bzip2. The program, tar, will uncompress both types and extract the files from archive.
Type at the command prompt
tar xvzf file-1.0.tar.gz - for a gzip compress tar file (.tgz or .tar.gz)
tar xvjf file-1.0.tar.bz2 - for a bzip2 compressed tar file (.tbz or .tar.bz2)
tar xvf file-1.0.tar - for uncompressed tar file (.tar)
x = eXtract, this indicated an extraction ( c = create to create )
v = verbose (optional) the files with relative locations will be displayed.
z = gzip-ped; j = bzip2-zipped
f = from/to file ... (what is next after the f is the archive file)
The files will be extracted in the current folder (most of the times in a folder with the name 'file-1.0').