Meat is a form of food made from butchered up animals, most of these animals only exist because of the need for meat. In advanced countries many or most farm animals spend their whole lives in cruel conditions on factory farms.
Many meat animals spend their lives in cruel factory farms. They suffer when they are transported in crowded trucks or trains to crowded livestock markets and slaughter houses, so most animals are quite grateful when they see the sign saying 'slaughter house'.
After that their deaths are usually relatively easy, their death often isn't perfect but the animals normally have a much quicker and less painful death than wild animals, many of which will die by being mauled to death by predators, and some may still be alive as they start to be eaten! Farm animals must be knocked unconscious before being slaughtered by law in most countries.
Some livestock farming uses grasslands and hilly or mountainous territory that is unsuitable for the growing of crops, or foodwastes that are unsuitable for human use. This has the effect of increasing the total food supply available for humans. Though hilly or mountainous areas could be used for forestry as well as livestock.
An increasing proportion of meat is produced by feeding animals either on crops that humans could eat or on crops grown on land that could have grown human food. The process of feeding food to animals and turning them into food reduces the total food supply, but increases the commercial value of that food. A world where many poor people go hungry while others eat to excess tends to be seen by progressives as an unfair world, and by Conservatives as evolution in action, the natural order of things, what was meant to happened because we are still at the mercy of nature.