The expression $a^n$ means $\underbrace{a \cdot a \cdot a \cdot\ldots \cdot a}_{n \text{ times}}$, where we
multiply $a$ by itself $n>0$ times. Note that $1^n=1$ and $0^n=0$.
The three laws of exponents are:
$\displaystyle{a^b \cdot a^c = a^{b+c}}$
$\displaystyle{\frac{a^b}{a^c} = a^{b-c}}$, and
$\displaystyle{(a^b)^c = a^{bc}}$.
These laws are explained in the following video:
Viewed as a function of $n$, the function $2^n$ grows very quickly after
a while, much faster than powers of $n$.