Q:

Are standing waves on a transmission line RF or DC?

I am very confused about Standing Waves on transmission lines.
Wikipedia says "a standing wave, also known as a stationary wave, is a wave which oscillates in time but whose peak amplitude profile does not move in space".
I'm getting the time domain and wave amplitude confused, I think.
I think I understand that a standing wave is caused by the superposition of the amplitude of a wave traveling in one direction upon that of one traveling in the opposite direction. In other words, the resultant wave caused by the addition and subtraction of amplitudes or 'interference' between two waves traveling in opposite directions. And that even though no one says it, they always mean the special case of two waves of the same frequency because one is usually a reflected wave of the other.
Is the voltage amplitude of a standing wave a DC value which you could measure with a multi-meter (with a theoretically infinite input impedance) ?
The pictures you normally see of standing waves which look like a sine wave, is this an instantaneous snapshot or does the amplitude of the standing wave actually stay fixed in space and time along say a transmission line ? 
Does the amplitude of the actual standing waves in space oscillate in time at the same rate as the two waves traveling in opposite directions ?
What else have I missed?

A:

Thanks for citing the Wikipedia item on SWR; as well as being a solid overview of the subject as presented in textbooks, the animations reveal much that is not obvious from a static description.

Is the voltage amplitude of a standing wave a DC value which you could
  measure with a multi-meter (with a theoretically infinite input
  impedance) ?

Wikipedia tells us that the voltages along the line are AC: 

"For example, the VSWR value 1.2:1 denotes an AC voltage due to
  standing waves along the transmission line reaching a peak value 1.2
  times that of the minimum AC voltage along that line."

The RF voltage along the line could be measured with an ideal rectifier and smoothing filter connected to a DC multimeter. Non-ideal rectifiers may produce misleading measurements at low voltages because their response is not linear below their knee voltage.

The pictures you normally see of standing waves which look like a sine
  wave, is this an instantaneous snapshot or does the amplitude of the
  standing wave actually stay fixed in space and time along say a
  transmission line ?

The "picture you normally see of standing waves which look like a sine wave" is borne out in the animation for the special case of $\Gamma$=-1:

SWR=$\infty$ results from dividing the peak value by the value of zero at the nodes.
There are several noteworthy features in the subsequent graphs for SWR values of 4, 2 and 9, respectively:

The superimposed forward and reflected waves form an envelope with "peaks" and "valleys"
The peaks and valleys are stationary ("standing") even though the underlying forward and reflected waves travel up and down the line
The higher the SWR, the greater the ratio between the peak and valley values of the standing wave

Does the amplitude of the actual standing waves in space oscillate in
  time at the same rate as the two waves traveling in opposite
  directions ?

Observing again the graphs, the forward and reflected waves have the same wavelength and, therefore, the same frequency, though they may be out of phase. While not explicitly stated in the Wikipedia item, the system is assumed to be linear, so there are no distortions which could introduce additional frequency components. Since linear combinations of signals of the same frequency can only produce resultant signals of the same frequency, the standing waves have the same frequency as the underlying RF signals that produce them.

