It consists of some form of fibreboard in various sizes and shapes (an unlikely 14 x 43" on the ones I measured) covered with an asphalt shingle-style tar and grit, pressed and printed into something and nailed onto the existing siding, giving the look of a brick house from across the street.
Definitely nearing the end of its existence...
but in looking around my neighbourhood, I see there is a variation that seems to be just a roll of asphalt shingle material 18" wide that people nailed onto the siding below. The lack of a fibreboard backing doesn't seem to have affected its longevity. Compare that to the life expectancy of "15-year" shingles available today.