A chain is a set of connected things, and it can be made out of various materials such as metals, wire, wood, rope, paper and many other, which is often used to bind,restrain or bond. It comes in various sizes and designs, while it is usually bought either per meter or per kg.
Working with chain can be from a very easy to a very difficult task, according to its material and size. Crafting chains are usually from aluminum and they are soft to cut with pliers and basic cutters. For heavier ones, there are special tools hand or foot operated as well as tools with heat.
Another definition is that a chain is a series of objects connected one after the other, usually in the form of a series of metal rings passing through one another, used either for various purposes requiring a flexible tie with high tensile strength, as for hauling, supporting, or confining or in various ornamental and decorative forms (source).