The basic difference between a layoff and a furlough is your relationship with your employer.
In a layoff, you are separated from your employer and a cessation of salary, healthcare, benefits, and seniority. Of course, there are exceptions based on prior contractual relationships. You keep an interest in your pension, but not in any uncompensated vacation or sick leave not taken or previously paid prior to layoff. You can apply for unemployment benefits and other assistance depending on your state's policies and requirements.
A furlough is similar to an unpaid leave of absence where you may retain your position, salary, benefits, and seniority. The company believes that the current situation may be temporary and you will return to your job. Depending on the company's policies, you may continue to receive your healthcare benefits or possibly pay a portion of the premium yourself. You may be eligible for unemployment benefits and other assistance depending on your state's policies and requirements.
Caveat: Be aware of the fact that the company's situation can change drastically and that a furlough can quickly turn into a layoff. In some cases, a company furloughs employees to remain eligible for state and federal assistance rather than lose access to taxpayer funds if you are laid off.
And consider that a company currently requesting voluntary layoffs or early retirement programs is often a precursor to involuntary layoffs.
Change is coming. There will always be a tomorrow, no matter how much you may try to ignore it. There are no guarantees in life or promises for a bright future. Just because something bad hasn't happened yet, doesn't mean it won't. It can happen to anyone, anytime, anywhere. No one is guaranteed to wake up tomorrow and still have a job by evening. Are you now wondering, Am I Next?