Recently I studied the definition of p-value as
The p-value associated with a test is the probability that we obtain the observed value of the test statistic or a value that is more extreme in the direction given by the alternative hypothesis, when $H_0$ (null hypothesis) is true.
For a two-sided alternative, the p-value =$P_{H_0}[|T|\geq|t_0|]$ where $T$ is the test statistic and $t_0$ is the observed value of the test statistic. Why do we take the absolute values of $T$ and $t_0$?