Agriculture describes the practice of growing crops or raising animals. Someone who works as a farmer is in the agriculture industry.
The Latin root of agriculture is agri, or "field," plus cultura, "cultivation." Cultivating a piece of land, or planting and growing food plants on it, is largely what agriculture means. Raising animals for meat or milk also falls under the category of agriculture. If we didn't have agriculture, we'd all be running around the woods, picking berries and trying to shoot things.