Multiple Sclerosis is a disease of the central nervous system (CNS). The central nervous system is made up of the brain and spine. Within the CNS there are lots of Nerves, these carry messages around the body. Coating the Nerves is a fatty substance called Myelin, this coating keeps the messages in the nerve pathways.
Multiple Sclerosis is classed as an autoimmune disorder, which means that your immune system helps protects your body from infections. Somehow your immune system thinks that the foreign object is the myelin that covers the nerves, therefore it damages the coating. This in turn destroys the messages, they can slow down, get disrupted or not get through at all.
When this happens, people with MS can experience symptoms, your specific symptoms depends on which nerve pathway is affected.
The link below leads to the national MS Society website, which has more information and a video about what is MS.
https://www.mssociety.org.uk/about-ms/what-is-ms
This is a video about “What MS is” from a young person’s perspective.