What is a ganglion?
A ganglion is a nerve cell cluster or a group of nerve cell bodies located in the autonomic nervous system.
They house the cell bodies of afferent nerves and efferent nerves. Ganglions provide relay points and intermediary connections between different neurological structures in the body such as peripheral and central nervous system.
An example could be in Octopuses, in which they have '9 brains', though the other 8 brains are ganglions found in their tentacles, which help them manipulate their arms and its many suckers.