there may be many abrasives that could be considered emery cloth.
it is usually cloth backed with abrasive glued to its surface, not to be confused with crocus cloth.
crocus cloth has the abrasive coating the backing, but not bound to the backing in the same manner as emery cloth.
the crocus, iron oxide abrasive, sheds easily in comparison in use
crocus cloth is sold in the fine, medium, coarse grades without reference to grit.
were emery is sold in grit variations
i generally use emery cloth for sanding munged up or rusty shafts.
i use either 150 or 220 grit for my needs
the last rolls i got were at HF.
i was pleased with the performance and cost of the HF emery cloth.
some things are a crap shoot at HF, but the emery cloths are decent products
the wet/dry abrasives are generally my goto gear.
3m and Norton make fantastic products, but you pay a premium for them.
if you do a lot of hard sanding, the more expensive products will perform better and last longer.