An important characteristic of such a spindle is the possibility to reach every point of the working range with any angle between tool and workpiece. A 5-axes-spindle usually has interpolating axes. This is, because routing is the most important application and routing in 5 axes is only possible with simultanuous movement of all axes.
There are special types of spindles with positioning rotational axes, where the drive of the C-axis also moves the A-axis (e.g.Flex5 and Vario NC. These are no real 5-axes spindles as only 4 axes can be moved at once.
Some machines have 5 controlled axes, but no real 5-axis-processing is possible. This may be the case, if there is more than one main spindle with C-axis or there is a tilting axis in conjunction with a C-axis.
See also: 4th/5th axis