People have always needed ways to cart their belongings around. In medieval times there were "coffers," large trunks carried by several people that held money, clothing or any number of things. This developed into the invention of trunks, smaller and more manageable pieces of luggage that could be carted in a coach or drawn in a cart by a horse. Initially the trunks had curved lids to keep water off; it wasn't until late 18th century that Louis Vuitton pioneered a flat-topped trunk with waterproofed canvas for traveling so that trunks could be stacked.
Luggage is used for carrying belongings in transit. Typically owners prefer luggage to be on wheels for easy transport. Luggage also can serve as an obvious symbol of status; name-brand luggage is common and expected among wealthier classes.
Some commonly seen options are duffel bags, rolling duffel bags, wheeled uprights, tote bags and wheeled bags. Basically all luggage can be seen on an intersecting scale among size, structure and space; in other words, a duffel bag can be very large and still fit within the airplane regulations but has little to no structure. A wheeled laptop bag is small and uses a considerable amount of its space for padding and reinforcement.
When purchasing a piece of luggage, consider first your price range as luggage can be either expensive or fairly cheap. Consider a size based on the length of travel it will most frequently be used for. Consider structure based on what will be contained within the luggage; delicate items should be carried in a highly structured unit like a wheeled upright or a trunk.
Always remember that there are strict regulations in effect for luggage on airline travel. Keep these regulations in mind so you don't purchase a bag so large as to always incur overage charges.
