Black ice doesn't actually sparkle when illuminated. That's the problem. It doesn't look wet, even in glaringly bright sunlight. At worst, the road surface looks clean. That's your tip-off, since the ground has to be very cold in order to get water to freeze so invisibly... so odds are there was a road salt layer everywhere. If it looks like the roads are pristine all of a sudden, get really suspicious. The change can happen very fast, even at a walking pace.

Glare ice is the same sort of icy glaze, but it is shiny and sparkly. This is much easier to see, and since you can see it you can take action. Glare ice can form in a wide variety of ways, and often melts easily. Melting is bad, since then the ice gets much more slippery. There is no way you'd miss glare ice when walking, even in cloudy weather.

People in climates where icing is rare won't often make a distinction between the two, since the end result tends to be the same.