All farms fall into one of two categories: crops or livestock. While some "crop" farms (like dairy farms or apiaries) do raise animals, the focus on move livestock farms is raising the animal for their meat. There are three main types of livestock farms in the United States: poultry (mostly chickens), beef (cattle), and pork (hogs).
While the focus on the crop farm is to grow as much of the product as possible without sacrificing quality, the focus on a livestock farm is to grow the animals as large as possible, also without sacrificing quality. Livestock farms range from small ranches that butcher just a few animals every week to supply the community to mass commercial farms which send thousands of animals to the slaughterhouse on a regular basis.
Like most crop farms, many livestock farms are owned by individuals who are contracted with a certain company, like Hatfield, Tyson, or McDonalds. These companies need their products to be as uniform as possible, so they give farmers a set of regulations to follow and require that farmers use certain equipment, feed, and pens. That's why a burger you eat at a fast food joint in Texas will taste the same as the burger you eat at the same fast food joint in Maryland, or even France.
Livestock farms are moving quickly to keep up with the consumer demand for "free range" or "grass fed" meat, though consumers have to be careful about looking too deeply into these terms, since they aren't strictly controlled by the USDA for every kind of livestock. Many farms, however, are realizing the benefits to entering these markets, so farms include both indoor and outdoor pens and cages. If you want to work on a livestock farm, be aware that your time could be spent indoors or outdoors.
Many livestock farms also have fields where they grow crops, though rather than selling the finished product, they use the grain to feed their animals. This is often more cost-effective than buying feed, so your work on a livestock farm could also mirror the work done on a crop-based farm. Check out that section of this website for more information on working in the fields.