There’s an entire philosophical literature around that, which is generally taken for granted when discussing consciousness. A good starting point is Thomas Nagel’s “What is it like to be a bat?”. The soundbitey version of his definition is that “There is something it is like” to be conscious - it involves a subjective experience - whereas for example there is nothing it is like (most people presume) to be a rock, or say an ordinary computer.

https://www.sas.upenn.edu/~cavitch/pdf-library/Nagel_Bat.pdf

He was talking in the context of the turing test, and here is a clear difference between the way Claude answers and the way a human would answer. So the turing test hasn't been passed. It's like he is trying to convince himself for some reason.