The numbers in the domain are the outcomes of the physical process tossing the dice. We cannot tell beforehand whether the outcome is 3 or 5 or any other number in this domain. This defines the randomness of the outcome, or unexpectedness or any other synonimous word which encompasses the uncertitude of the final outcome.

The only thing we can tell beforehand is that say the outcome 2 has a certain probability. If our favorite hobby is to spend an hour every evening throwing dice and registering the sequence of outcomes, we will note that the numbers in the above domain $$ \begin{equation*} \{2,3,4,5,6,7,8,9,10,11,12\}, \end{equation*} $$ appear in a random order. After 11 throws the results may look like $$ \begin{equation*} \{10,8,6,3,6,9,11,8,12,4,5\}. \end{equation*} $$