the reason why ambulances have the word AMBULANCE written as mirror writing on the front of the vehicle is so that drivers (of cars driving in front of them) would be able to see the word the right way around in their rear-view mirror?
Some people are naturally good at mirror writing. Leonardo da Vinci for example wrote most of his personal notes in this way. But it is a phase that most of us go through in childhood. Unintentional mirror-writing is surprisingly common amongst young children (and also in brain-damaged adults) as the brain doesn’t completely form the concept of left and right until somewhere between ages five and eight. Many parents have personal experience of this, and it is always an amusing discovery. So if you wonder why your five-year old son wrote his name akin to OCRAM, that is the reason.
Here an interesting video on the subject: