What is Spirituality?

Bhagawan Ramana Maharshi has put it in four simple words.
Deham (देहं)
naaham (नाहं).
Koham (कोहं)?
Soham (सोहं).

What does it mean?
Deham naaham = I am not this body
then,
koham? = who am I?
soham = I am That