That said, common chords are A, B, C, D, E, F, G (and their sharps and flats), combined with either major or minor mode. Hence "C, G, F, Am, Em" is an example of what someone could play. Now, of course, if it doesn't sound exactly like a G, perhaps it's a G7? After some practice, you can even hear, by the sound of the strings, exactly which chord it is. Em, G, and D are particularly simple to recognize.
Each interval has a unique "flavor" and once you can hear them you should be able to hear multiple intervals at the same time, which effectively identifies the chord. (Admittedly for complex jazz chords it can get very difficult and you probably need more powerful tools, I can't say.)
Kinda, but on Guitar, most pop songs are major/minor, possible sevenths. I think this post is aimed at someone who can read tab, but isn't "good" (what ever that means) so they should have an understanding of basic chord shapes.
The post does imply that this only really works if you can comfortably read tab, which is probably 6month-2 years of work (part time)
Even if they're not exactly what was played, you'll be able to get to a working version with the right idea.
In any case, theory and experience will narrow the field down a great deal so you're not just stabbing at things in the dark.
The point is not a perfect outcome. The point is the effort.