Memory Card Specifications and Nomenclature

[ameerat42]

How to sort out the mess of terms relating to memory cards in terms of physical size, capacity, speed,
and anything else that's pertinent.

Apologies for the longish title and even longer sub-title.

I was recently looking for a suitable micro-SD card to take 4K video with the Samsung Galaxy S5 phone camera.
At first I thought I had a "reasonable grasp" of it/the main points/something-or-other to do with it. A recent thread
I replied in has made me realise that it's not as simple as I had thought.

Of the two main types of card, CF (Compact Flash) and SD (Secure Digital), I'm concentrating more on the latter
with references to on-line info.

The most comprehensive, all-in-one-place reference of the 10 or so found just today is this Wikipedia article.
It's long, and what I thought was "some fair knowledge" on my part turns out to be a small part of what's here.
At least it wasn't "wrong", just incomplete.

Anyway, feel free to add to this thread with any insights on the topic, not necessarily restricted to just SD and CF
cards.