In these stotras, written in his supreme state of realisation, Adi Shankara explains the state of wisdom and truth.
When Adi Shankara was in Kashi, he used to have his daily bath in the Ganga.
One day, on his way to the Ganga, his way was blocked by a Chandala (belonging to the untouchable caste) whose job was to burn the dead bodies.
Adi Shankara immediately asked him to go away.
The man, instead of moving away, asked Adi Shankara `who are you?'
Adi Shankara knew that no ordinary man would ask him this question and he realised that the man in front of him was the Lord Kasinath Shiva himself.
Searching for an answer to the question `who are you?'
Adi Shankara went into a deep state of meditation.
And being in the state of highest consciousness, he identified himself with the ultimate truth of life -- Shivoham.
Shivoham means `I am Shiva'.
He wrote down his answers then and there and read it out.
Adi Shankara mostly answered the question "who are you" by saying what/who is not he, instead of just saying who is he!
Adi Shankara was no ordinary soul to have attained the state of `Shivoham' at a very young age.
What lies between realities and false identification is the truth. The truth, the ultimate truth is Shiva.