Think of a tar file as bein glike a zip file. It's just a compressed file. It has to be "unzipped" or untar'd using gzip. Then you can run the ./configure and install. To extract the standard is pretty much this.
tar -xzvf [name of file.tar.gz]
The .gz refers to the gzip method, you'll also see .bz2 files that use bzip2 which is a bit better compression resulting in smaller files.