A machining center is a CNC machine that mills, drills, and taps with an automatic tool changer, so it runs many operations in one setup. They come as vertical (VMC), horizontal (HMC), and multi-axis configurations. It's the workhorse of most metalworking shops.
See every Vertical Machining Centers in the reference library, by make and model.
How this affects buying and selling: read The Gauge, or value any machine free at The Machine Blue Book.