A piglet is any young pig, while a litter is a group of piglets born together. The smallest piglet in the litter truly is called the runt, while any pig still nursing is called a sucker. The time between birth and weaning is known as farrowing, and young pigs that are weaned are known as shoats.
History
All of the hundreds of breeds of domesticated pigs descended from the Eurasian wild boar, a native of Europe, Asia, and Africa that has spread almost worldwide. They resemble domestic pigs, and they are considered the same species because they can still interbreed, yet there are several distinct differences between wild and domestic pigs. Boars have longer hair and tusks than most domestic pig breeds. Most notably, their front legs and shoulders are much more muscular, with leaner hindquarters, whereas domestic pigs have much more muscular rear halves.