Sometimes we have to write a report about something we have seen or done. If there has been an accident at your workplace you can write a report to your boss. Then he/she will know what happened, and why it happened. A report may be used to place responsibility for an accident, to change routines or to decide whether a person should get some compensation for an injury.
(Background. Why are you writing this report?)
(What happened? Who? When? Where? Facts, not opinion)
(What do you think caused the accident? / What should have been done differently?)