Those not in the medical field typically don't have to worry about Faxing things. It is a very old method of sending information on a piece of paper from one place to another. Today most people text or email that information. Hospitals, along with a few other institutions, still relay heavily on this old slow process of moving data.
Here is a fun fact, in case you find yourself in need of a fax machine.
There are over 17 million fax machines in the US, or one about every 4.47 square miles.