Concentric cable is generally used by DNOs to supply most modern cutouts, but it's use is not exclusive to DNOs.
There are two different types of concentric cable. Their selection / use depends on the supply type.

This is a DNO cutout supplied by a straight concentric cable.


(This is a TN-C-S supply)

This is a DNO cutout supplied by a split concentric cable.


(This is a TN-S supply)

Some pictures of split concentric kindly provided by Lectrician


The cable with the sheath stripped back


After its prepared; the earth is sleeved as two separate bits to keep it tidy


25mm² Split concentric terminated in a consumer unit through a bush and locknut