Direct vs indirect (ie within 60 days) rollovers. See below link for further.

https://www.irs.gov/retirement...nd-ira-distributions

Direct is much cleaner but you’ll need to provide the detailed payee info to the old plan trustee so that the distribution is directly remitted to the new plan trust.

I'm actually in the process of setting up a direct transfer with my financial advisor. I'll need to wait until after my 65th birthday in July.