What's the difference between a lathe, a screw machine, a truning center, and a CNC lathe?

In its simplest form, a lathe is a machine that can make turned parts from bar stock, but has no milling capability. Screw machines, turning centers, and CNC lathes are lathes that have the ability to turn and mill parts. Turning centers and Swiss lathes can typically make more complicated parts than screw machines, and are better-suited for parts with tight engineering tolerances. Swiss lathes tend to be better for small, thin, and long parts than screw machines and turning centers.