If you found your self in an emergency situation or you were out camping or even bugging out and food is sporadic, the purpose is to preserve these protein-rich foods, which would otherwise spoil quickly, for long periods.
You can smoke pretty much any red meat and fish. I found a great article showing you how to make 3 different styles of smokers, dependent on what you have available. Obviously there are other ways to smoke meats too but this is great knowledge to have stored just in case you need it.
Photo Credit: meatsandsausages.com