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

Our team was told about a closure date that is 13 weeks away. 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.