Agriculture was the step that enabled humans to move beyond the hunter gatherer stage. Agriculture is the planned cultivation of plants and animals. It has given mankind the surplus of food needed to develop cities that would allow people to specialize in none food related production. Ever since the beginning of agriculture the species being grown have been selected to improve their characteristics. The best ram was kept to improve the goat herd, or the largest heads of wheat were saved to plant next year. Over millennia this selective breeding has led to many of the varieties we are familiar with today.
The industrial revolution was the major step away from an agricultural society. As cities grew larger and there were fewer farmers the farmers needed to produce more and more food. Agriculture did benefit from the industrial revolution. Initially it was largely the textile industry that benefited from inventions like the cotton gin and other processing machines.
The two areas of agriculture are the cultivation of plants and the cultivation of animals. For much of human history these two types of agriculture were difficult to separate. The horse ate the hay that grew in the field that it cultivated in the spring and harvested in the fall and fertilized with it's manure. Farms operated nearly independent of external inputs. The farmer produced what they needed to eat and sold excess to earn some money to purchase the things they couldn't produce.
Today even more thought and research is put into the development of new strains of a crop. Companies spend millions of dollars to protect their specific hybrid of a crop or animal. There is much concern today about the control of agriculture in fewer and fewer hands and what they may be doing with the future of our food. Genetically modified crops have been appearing on the market recently to no shortage of concern. The modern day intensive farming has many drawbacks, but some of the positive aspects are that they produce large quantities of food to supply the world.
There is a growing movement of people towards more sustainable forms of agriculture. This movement wants to see less destructive farming methods used to produce the food that is eaten. Some of the driving force behind this is the amount of information coming out about how much less nutrious our food is today than it was thirty years ago.
This can easily be seen by the rise of organic and natural products becoming available in mainstream grocery stores. It can take a serious commitment to this type of lifestyle since the products are generally more expensive, unless it's produced at home or even locally.