Confused on Vanguard settlement fund

I recently just got let go from my job (by recent I mean like 2 hrs ago lmao). I was thinking of rolling my traditional work 401k to a traditional IRA through vanguard until I get a new job. I have about 7k in my 401k as of now.

But my question is what is a settlement fund? Vanguard is having me choose between Cash Deposit or Money Market. Why do I need to put the money here? And which of the 2 is the best option for my situation?