It is a law that says that a worker who is injured on the job gets compensation. Almost all employers are legally required to have insurance to pay the compensation.
Work accidents are common.
Under traditional legal theories, the worker had to prove that the injuries occurred because the boss was at fault. The problem was that the boss was normally not at fault. In those rare cases in which he was, like requiring the worker to use a rickety ladder, the worker still had to sue the boss to get compensation and when that happened, he would normally lose his job. Worker compensation was established to protect the injured worker. The law excludes these workers so that their employers do not have to pay the high premiums for workers compensation insurance.