What is the definition of$\mathcal{Mod} P$ counting complexity class? Question : What is the definition of $\mathcal{Mod} P$ counting complexity class?

I am not getting anything relevant about this complexity class on Google search. If it is available on Wikipedia, please share a link.

$\mathcal{Mod} P$:  A set $L$ is in the class $\mathcal{Mod} P$ if there exist functions $f \in \#\mathcal{P} $ and $g \in \mathcal{FP}$ such that string $x$, and $g(x) = 0^p$ for some prime $p$ and 

$$x \in L \iff f(x) \ncong 0 \pmod{p}\,.$$ 

I am not able to understand what it is mean by  $g(x) = 0^p$ for some prime $p$.

Reference  : K&ouml;bler and Toda, On the Power of Generalized MOD-Classes. In Proceedings of 8th Annual Structure in Complexity Conference, IEEE, 1993. PDF
The class ModP is defined in Definition 3.1 on page 3 of your reference.

The abstract of the paper clearly states that the paper studies the computational power of the new counting class ModP. This suggests that this class is introduced in the paper, and in particular, is defined in the paper.