Mystery is, not knowing the truth about some event that happened or about a person. For example, we do not know what happened to Subhash Chandra Bose. His life ended in a mystery. We do not about the life after death and what happens after. It is a mystery.
There are many mystery bestseller novel writers in all languages world over. The sense of mystery really intrigues people and they like it. People watch films and TV serials thrilled by the mysteries. If the mystery is broken, then they will lose interest. The nature was a mystery to man and woman for a long time.
Scientists over centuries have unraveled the mysteries of the world in various fields of sciences. Mysteries are everyday lives for the police force and detectives. For many people, their own lives are a mystery until they settle down somewhere.