'Made from scratch'?

You know, all my life I've heard about food being made from 'scratch'. I am so amazed at how versatile this 'scratch' stuff is! I mean, apparently you can make anything from rhubarb pie to beef stew from 'scratch'. My problem is that I have never actually seen 'scratch'...I've never seen it in the wild, on a farm, or sold in stores anywhere. Where can I find it? Does it grow only in certain parts of the country? What is its scientific name?