PWM vs Analog Signals
[General remark:  Treat hobby-grade sources like SparkFun with a pinch of salt.  Their objective is to make things easy, fun, exciting, practical without getting bored with integrals and derivatives.  As a result, you get loose statements occasionally.]

In some books, PWM is called a pseudo-analog signal.  It has only high and low voltage level, but timing is continuous.  Timing is either truly continuous, or it has high enough digital resolution where it can be considered continuous for practical intents and purposes.  When PWM is converted to an actual analog signal, that's always done with a low-pass filter of some sort.  Here's are some examples:


So called "poor man's DAC", which consists of a PWM output from a microcntroller followed by a low-pass filter.
Buck converter
Class D amplifier