Quick answer
A covered conductor has an XLPE covering bonded over an overhead line conductor — enough insulation to survive touching a branch or another phase, but not rated as full insulation, so it is still treated as a live overhead line. A cable is fully insulated and screened for its voltage and can be buried or ducted. The covering is what removes the majority of overhead-line faults: clashing in wind, vegetation contact, birds and animals. APAR covered conductors span 11 kV to 132 kV — see the MVCC selection guide.