Let’s look at an example for this by considering:
\begin{equation*}
H_0: p = 0.20
\end{equation*}
vs
\begin{equation*}
H_a: p \ne 0.20.
\end{equation*}
Tests like this are called two-tailed since there are two ways to reject the null hypothesis: we find that p should be less than 0.2 or we find that p should be greater than 0.2.