There is talk of 'central glia' and of 'peripheral glia'.
The central glia occurs in the CNS in four (five) different variants:
1/ astrocytes
2/ oligodendrocytes
3/ microglia
4/ ependymal cells
(5/ Choroid plexus cells)
The peripheral glia occurs in the PNS in two different variants:
1/ Schwann cells surrounding the axon in the PNS
2/ Satellite cells surrounding the nerve cell bodies in the ganglia
The glial tissue has long been perceived as a kind of support for the nerve cells and their protrusions; This is partly by mechanically acting as support, isolation and protection, and partly by relieving the neuron of certain tasks within metabolism.
Recent research suggests that certain glial cells, astrocytes, may be directly involved in information dissemination and memory storage.
Usually, the number of glial cells in the brain is stated to be 5-10 times as large as the nerve cell count. Nowadays, the number of glial cells in the brain is considered to be significantly lower and more or less correspond to the number of nerve cells. The explanation lies in more recent calculations of the presence of gia cells in the cerebellar grain cell layer , where almost 20 neurons run on 1 glial cell.
Yuhas, Daisy, and Ferris Jabr. "Know Your Neurons: What Is the Ratio of Glia to Neurons in the Brain?." Scientific American, Brainwawes. June 13, 2012.