I see these in the stores, usually fluffy white overly plush “spa towels”.
Where does micro fit into that?
If the fibers are short then the towel can’t be very thick.
If the fibers are thin they can’t be cotton.
Microfiber is a blend of polyester and polyamide. Microfiber cotton towels are a blend of microfiber and cotton; thus the thickness is determined by the manufacturer.
I don’t know about trade names in the textiles industry, but more generally microfibers are small fibers. For example, HEPA filters are made of glass microfibers. For another example, a company named Freudenberg has for years been selling nonwovens made of polypropylene microfibers. In these contexts “micro” has a somewhat vague meaning suggesting that the fibers are less than around 10 micrometers and maybe less than 1 micrometer in diameter.
The vigor with which a porous medium can extract from its surroundings liquids for which it has affinity increases with the fineness of its structure, so a “microfiber” version of a towell should get you drier.
There are numerous strains of cotton plant. I read not long ago about different cottons being bred to have different color, for example, and know that different cottons have different staple lengths. Probably, there are strains of cotton that have coarser or finer fibers, though I don’t know, and don’t know if that’s what is meant by the cite.
To me miicro fibre towels are for trekking not luxury spas! Micro fibre towels are soft and somewhat fluffy - like a cotton towel - but are very light, fold up small, and dry very quickly.