What are glial cells?
Glial cells differ from neurons because they do not directly send electric signals. If you think of Nascar racing, neurons are like race cars and glial cells are like the maintenance crew checking the car's oil levels, tire pressure, and engine function to make sure the car runs smoothly.
In the case of glial cells, they support neuron functions by helping to maintain homeostasis (or balance in the system), regulate the rate of nerve signaling, and aid in recovery after nerve injury.
What are the different types of glial cells?
Oligodendrocytes (krab roll with fish skin) - In the CNS, oligodendrocytes' main function is to support a neuron by producing myelin (squid nigiri). Myelin is really important for rapid neuron communication. In the peripheral nervous system, these glia are called Schwann cells. The main clinical conditions associated with dysfunction of oligodendrocytes/Schwann cells is multiple sclerosis.
Astrocytes (bigger octopi) - These cells have many functions; most importantly, they help the neuron by maintaining ion balance, providing nutrients, and repairing after injury. Clinical conditions associated with dysfunction of astrocytes are traumatic brain injury (TBI), stroke, and CNS infections.
Microglia (smaller octopus) - These cells are the cleanup crew; they act as macrophages to get rid of a wide variety of unnecessary substances that might harm the neuron. Clinical conditions associated with dysfunction of microglia are neurodegenerative diseases and TBI.
Ependymocytes (not pictured) - These cells line central nervous system tissue in the brain's ventricles, or hollow spaces. Their main function is to produce and regulate cerebral spinal fluid.
 Bear, Connors, & Paradisio (2015). In Neuroscience: Exploring the Brain (4th edition)
 Banich & Compton (2018). In Cognitive Neuroscience (4th edition)
 Hagan, C. E., Bolon, B., & Keene, C. D. (2012). Nervous system. In Comparative Anatomy and Histology (pp. 339-394).