Management-Buy-In (MBI)

The term management buy-in comes up regularly during a business acquisition. But what exactly does it mean and how does this differ from a management buy-out (MBO)?
An MBI is the acquisition of (part of) a company by one or more persons who will take over (a part of) the control of the company themselves following the acquisition. An MBO is an acquisition of (part of) a company by the current management and possibly other staff, either with outside financing or otherwise.
The difference, therefore, is whether the company's buyer was already involved with the company prior to the acquisition.