Trauma is defined as "emotional shock following a stressful event or a physical injury, which may be associated with physical shock and sometimes leads to long-term neurosis."(1)
PTSD - Post Traumatic Stress Disorder - is a very common health condition that develops following a traumatic event.
Trauma and PTSD can be caused by a variety of factors including injury, hospitalization, car accidents, abuse in any form, and neglect. However, even small "normal" events can cause trauma, such as a young child feeling abandoned at school if they were not ready for the experience.
(1) Mirriam Webster