Layoff notice, what does the 60 days mean? (Providence)

I received a formal notice about a mass layoff at my workplace. It has been a long 3 weeks. I do not know if I should start looking now or wait for severance news. Should I stay for the bonus?

Thanks for writing this out. I went through something close to it last year, and it settled down once I kept a simple log of every call and form.