To use a Windows metaphor: Think of tar.gz files as .zip files. They can contain just about anything, from pictures to installers to source code to viruses. They don't necessarily do anything by themselves, you need to extract the files and then work with the contents. Browse through the extracted folders and files and look for instructions. Normally there will be a README file, that is where you start.
If you are working with source code, you need to configure, compile and install using the root account. This is one of the easiest ways to bork a system.