Star notation for context-free language alphabet?
It is equivalent (usually, otherwise it would be explicitly stated).
The &quot;star-operation&quot; is called a Kleene-star, and it is an operation that basically takes the set and creats the set of all combinations of items from the original set. In the example of $\{0,1\}$, we would have that $\{0,1\}^*=\{0^{k_1}1^{k_2}0^{k_3}\dots\mid k_1,k_2,\dots\in \mathbb{N}\}$, and intuitively speaking, this is the set of all words created from the alphabet $\{0,1\}$. This obviously is also true for any other alphabet $\Sigma$ you would want.