This is the motto of the American Mountain Men, Inc. Essentially it means "to live from the land" or "to survive off of the land." The fur trapper or "Mountaineer" of American western history became an expert in wilderness survival. They learned much from the Native Americans and they brought prior knowledge with them. Within a short period of time they had to master many skills of survival or perish in the beautiful but unforgiving environment.
Today we try to master those same skills. It's not so much that we need to for daily survival but because in doing so we gain an appreciation for our environment, a better understanding of what life was like for our forefathers and in fact we do often place ourselves in situaitons where such skills are needed for immediate survival.
Below you will find a variety of links to web sites that will give you much information on wilderness survival. But keep in mind this is only "book learning, " to really master the skills for practical use, it takes time out in the wilderness applying them. What we like to call "getting out on the ground."