1. Basically, it's just a calibrated EQ boost applied to the recording and then a calibrated inverse filter (EQ cut) applied during reproduction. In the case of CD pre-emphasis, it was a high freq boost/cut, +10dB by 20kHz. TBH, I'm only going on what I've read about the history of digital audio, I have no personal experience of pre-emphasis. It's use was already long dead when I started in the sound engineering business (beginning of the '90's).
1a. Before redbook was ratified, 14bit was expected to be the bit depth of CD but redbook ended-up being specified as 16bit. Although CD was launched to consumers in 1983, specifications for it started the mid '70's and the redbook specs were published in 1980. Now it doesn't sound like much of a time difference but it was a monumental time for digital technology. As companies started to realise digital tech was going to revolutionise society, there was a massive R&D push to not only invent/design chips with greater functionality but also produce them in mass numbers for public consumption. In other words, the redbook specs were published according to the digital tech that existed in the late '70's but by the time CDs and CD players actually started being manufactured for consumers, the available tech had already vastly improved. For example, in the late '70's there was no digital dither or digital filters; dither was effectively just added analogue white(ish) noise, not the statistically perfect, mathematical representation of it that's possible in the purely digital domain and anti-alias and reconstruction filters were also all analogue, plus there was no oversampling. These analogue filters were relatively very "noisy", as it''s pretty much impossible to create a very steep analogue filter without significant artefacts. However, by the time consumer CD players were released, they were pretty much all capable of 2 times oversampling, allowing cheaper and much less noisy analogue filters and within a few years digital dither was available and the filters also became digital. In other words, much of what is "digital audio" was, at the time when rebook was agreed and published, still analogue and "Emphasis" was included to help reduce the noise of these analogue processes. However, much of the need for "emphasis" no longer existed by the time CDs actually hit the streets and by the mid '80's there was no benefit at all (and was effectively dead). BTW, noise-shaping first became available in the early '90's (Sony's "Super bit-mapping", I believe) and was standard practice by the late '90's.
2. Yes, in concept it was exactly the same thing, although the actual EQ (curve) applied is different.
I appreciate that, as it's always a potential issue when explaining something in layman's terms. I myself could find loopholes in what I've stated, not because it's intrinsically wrong but because any simplification or "layman's terms" is by definition an interpretation and can therefore be misinterpreted by the reader. Disputes can therefore arise which effectively derail the discussion because they're often disputes about the choice of wording and semantics, rather than the actual facts.
G