Workers' compensation is a system designed to compensate you if you are injured or become ill at work. It acts in place of a lawsuit against your employer. Each state has its own workers' compensation system. Every system is a little different, but there are similarities. To get the money to pay benefits, employers buy workers' comp insurance, required by most states.
Federal employees have a separate workers' comp system, which is similar to most state plans.
Work with an experienced lawyer in your state.