Basically, if you're salaried (Full-time employee) and an executive gets a hair and decides to pivot, then layoffs'll happen. Basically, it's your employer looking at financial prospects and going "We no longer have need of your services."

It is generally coupled with a severance package, which if taken delays your eligibility to avail yourself of your State's unemployment benefits. Many states are at will employment. It is customary to give two weeks notice, but not strictly required.

The U.S. can be a fickle beast.