Short answers, pulled from the story.
Subsistence agriculture is a farming system where farmers grow crops on smallholdings to meet the needs of themselves and their families. Tony Waters defines these individuals as people who grow what they eat, build their own houses, and live without regularly making purchases in the marketplace.
Subsistence agriculture largely disappeared in Europe by the beginning of the twentieth century after market-based capitalism became widespread around 1800. It began to decrease in North America with the movement of sharecroppers and tenant farmers out of the American South and Midwest during the 1930s and 1940s.
In 2015 about 2 billion people slightly more than 25% of the world's population lived as smallholder farmers in rural areas of developing nations. These 500 million households work less than 2 hectares or 5 acres of land.
Most subsistence agriculture is practiced in developing countries located in tropical climates where extreme temperatures link to lower crop yields. Rates of production for cereal crops like wheat oats and maize have been declining largely due to heat's effects on crop fertility.
Shifting agriculture involves clearing forest land by felling and burning before crops are grown while sedentary farming involves smaller fields near the homestead. Nomadic herding sees people migrate along with animals like cattle sheep goats camels and yaks in search of fodder.