PTSD is a psychological condition that's caused by a traumatic event in a person's life. It's not uncommon for soldiers who've fought in wars to suffer from PTSD long after the war has ended.
You can use the acronym PTSD for the disorder officially known as post-traumatic stress disorder. It's a complex condition that can last for years and have symptoms (like anxiety, extreme anger, and trouble sleeping) that make it hard for people to live normal lives. Being abused, witnessing violence, or living through a natural disaster are all traumatic events that can lead to PTSD. This disorder is treated with therapy and sometimes medication.