Alternators

In my book it says "a variation of the revolving armature AC generator is often used for very low power (e.g. An automobile alternator) where both windings are interlaced on a stator and the fields are coupled by a rotating soft iron (electromagnetic) armature without windings."

I don't understand what they mean by "both windings"? And why are they interlaced? Also, how does an armature operate without windings and how is it electromagnetic?

Very low power is a matter of perspective. Auto alternators can run 100+ amps and if not regulated the voltages can easily exceed 120 volts. Remember that when making a general statement covering a common item like an alternator there are many variations in use. A single winding alternator could simply be a permanent magnet alternator, with a permanent magnet rotor and interlaced stationary winding or stator. The interlaced part refers to how the A B C windings are mounted in the stator. The use of the word armature when referring to an auto alternator should be discouraged. It creates confusion due to the fact that the rotating armature in a generator becomes the stationary winding in an alternator. So rotor and stator are the accepted terms. Now all that said there are variations of "alternator" that do more sophisticated things and the term "armature winding" comes back into use. At this point it can be rotating or stationary but it provides the function it originally did in DC generator. These generators would generally not be considered low power or simple as they may have multiple armature and field windings and they may be rotating or stationary, the terms armature and field simply refer to the fact that the winding is either creating a magnetic field or creating electricity from a magnetic field.