Castors are essentially wheels, mounted onto an object that needs to be moved easily and efficiently. There are many different kinds of castors, from the kind you would find attached to smaller, lighter objects, through to the kind you would find used on heavy, industrial objects for industrial applications.
In short, castors are used for ease of movement and to improve safety. In an industrial environment, anything that makes lifting, loading and moving easier is a step towards better safety in this kind of environment. They will be permanently fitted to an object, usually by screwing it in, and they will be used to manoeuvre the object from place to place. This is especially useful in an industrial setting, where safety is paramount and people at work need to be well protected. You can find different kinds of castors for different settings, so choosing industrial castors will ensure they are the right kind for their environment and usage.