I’m going through this process right now. A rollover is when you transfer your vested funds from your company’s 401K retirement savings account into a 401K at another company, or to an IRA when you retire. An IRA (Individual Retirement Account) is your own personal retirement savings account at the financial institution of your choice, and it, like the 401K, shields your savings from taxes as long as the money remains on deposit. There’s a lot more to know but this, but this is the basic explanation. Hope this helps.