  Let $G=(V,E)$ be a simple graph. A function $\phi:V\rightarrow \mathbb{N}\cup
\{0\}$ is called a configuration of pebbles on the vertices of $G$ and the
quantity $\sum_{u\in V}\phi(u)$ is called the size of $\phi$ which is just the
total number of pebbles assigned to vertices. A pebbling step from a vertex $u$
to one of its neighbors $v$ reduces $\phi(u)$ by two and increases $\phi(v)$ by
one. Given a specified target vertex $r$ we say that $\phi$ is $t$-fold
$r$-solvable, if some sequence of pebbling steps places at least $t$ pebbles on
$r$. Conversely, if no such steps exist, then $\phi$ is $r$-unsolvable. The
minimum positive integer $m$ such that every configuration of size $m$ on the
vertices of $G$ is $t$-fold $r$-solvable is denoted by $\pi_t(G,r)$. The
$t$-fold pebbling number of $G$ is defined to be $\pi_t(G)= max_{r\in
V(G)}\pi_t(G,r)$. When $t=1$, we simply write $\pi(G)$, which is the pebbling
number of $G$. In this note, we study the pebbling number for some specific
graphs. Also we investigate the pebbling number of corona and neighbourhood
corona of two graphs.
