Layoff notice, what does the 60 days mean? after 14 years as a project coordinator

My employer announced that the site will close and gave us written notice. I do not know if I should start looking now or wait for severance news. Has anyone been through this?

I stayed for the retention bonus and looked for work on the side. It cushioned the gap.

Write down key dates and keep copies of the notice. Mine helped when a question came up later.