A more thorough explanation:

A pro-con debate is a type of debate where speakers take turns presenting arguments for or against a motion or proposition. The goal is to persuade the audience or the opposing side to agree with their point of view.

For example, in a pro-con debate about whether or not to legalize marijuana, one speaker might argue that it should be legalized because it has medical benefits and could generate tax revenue. Another speaker might argue against legalization, citing concerns about addiction and negative effects on public health.

The alternating speeches in a pro-con debate help ensure that both sides are heard and that the audience can make an informed decision. However, sometimes one side may have more speakers than the other, in which case the chair may allow multiple speeches in a row from the same side.