Employee vs. independent contractor
The difference isn't always clear. There are many factors to consider, including whether you have taxes taken out of your pay check, whether you can come and go as you please or if you have a schedule, whether you have a uniform, whether you have tools or other equipment given to you, and how much instruction your employer gives you in performing your job. Basically, the more control your employer has over you, the more likely you are to be considered an employee.
Your employer doesn't get to decide
It's not up to your employer to decide whether you are an independent contractor for the purposes of workers' compensation. They may tell you you're ineligible, but just because a piece of paper labels you as an independent contractor doesn't mean it's the case. If there is a dispute, the Illinois Workers' Compensation Commission will decide based on the factors listed above.
How an attorney can help
The law in this area is designed to prevent employers from avoiding the workers' compensation insurance requirement. However, they may try to avoid it anyway. If you believe you are treated as an employee, an attorney can help you prove it.