What does Socrates mean when he said Know thyself?

"Know thyself" is not an easy thing to do.

Each of us has multiple persona's that we use depending on who we are with. i.e.; How I "present myself" to other people or "the whole world is a stage."

Actually knowing yourself takes years of soul searching and insight. You need to strip away all of the multiple personalities that one puts on for different people and get down to the core of your essence. Then you need to get rid of your own false self-images and delusions.

There is a big difference between:

"Who am I?" and

"Who do I think I am?"