When talking about chords, chord symbols and harmony from a Western music point of view, something called a stack of thirds is often mentioned. What does it mean? Isn't it a chord voicing - maybe even, just one type of chord voicing? Why is a stack of thirds mentioned when talking about chords in a seemingly theoretical discussion, chord symbols...?
This is already answered and accepted, but I'd like to raise this great comment about different harmonic styles by user leftaroundabout. It would have been nice to have this as part of one of the answers, but I'll put it here. This somehow clarified the different perspectives for me:
I strongly disagree that “the vast majority of chords used can be figured this way but the order of those component notes - the voicing - doesn't detract from the fact that they contain stacked 3rds”. Many chords in common-practice music don't make sense without the voice leading context, and hardly benefit from a thirds-stack interpretation even when that is possible. Many genres use chords that simply can't be rearraged to anything thirds-based (e.g. because of microtonality). Honestly, I'd say only in Jazz-related music is it useful to think of chords as stacks of thirds.