Layoff notice, what does the 60 days mean? - what worked for you?

I received a formal notice about a mass layoff at my workplace. This is my first time dealing with any of this. I do not know if I should start looking now or wait for severance news. Has anyone been through this?

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.