automata – Star notation for context-free language alphabet?

It is equivalent (usually, otherwise it would be explicitly stated).

The “star-operation” 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 $${0,1}^*={0^{k_1}1^{k_2}0^{k_3}dotsmid k_1,k_2,dotsin mathbb{N}}$$, 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 wod want.