A turning center is a CNC controlled lathe.  Like most lathes, the workpiece is held by a chuck or collet, but the movement is computer controlled to ensure higher accuracy and efficiency.  The ability to program gives turning centers more versaility and efficiency than manual tool room and engine lathes can.  Some turning centers are further augmented with twin or sub spindles and and two turrets so that a workpiece can be machined on multiple faces, providing great savings in terms of setup time and efficiency.  The work that might require multiple machines and extra setups can be done with a single machine tool.