Sorry for offtopic, but I find it strange that so many people find it hard to remember, it's just: e(x)tract, be (v)erbose and use (f)ile. If it was gzipped add -z. If you're compressing the file use -c (for compress) instead of -x. To me it was one of the easier commands to memorize...
tar -xf archive.tar # Extract all files from archive.tar.
If you work with lots of different types of archives or have a hard time remembering the various tools and arguments, I recommend dtrx (Do The Right Extraction). Super simple and it ensures you don't accidentally dump a whole directory tree somewhere it shouldn't. Assuming you have pip and hg installed, you can install the latest version to your user site with the following command:
I have to google the extract arguments for tar every single time I use it. What was it again, -xfv?