Final answer:
Schwann cells are the type of glial cells that myelinate only one axon each, with multiple Schwann cells needed for each axon, providing insulation in the PNS.
Step-by-step explanation:
The cells that myelinate only one axon each, with multiple such cells being required per axon, are known as Schwann cells. Schwann cells are different from oligodendrocytes as they wrap around a single portion of an axon segment and no others, providing insulation with myelin in the peripheral nervous system (PNS). Each Schwann cell surrounds just one axon segment with its nucleus and cytoplasm on the edge of the myelin sheath. In contrast, oligodendrocytes are found in the central nervous system (CNS) and are capable of insulating multiple axon segments with myelin, either from the same or separate axons.