What are the main differences between directly and indirectly transitive verbs in French and why is it important to distinguish between them?

A transitive verb is simply a verb that takes an object. However, there are two types of these: directly transitive verbs are those that take a direct object pronoun (e.g. rencontrer qqn) , and indirectly transitive verbs are those that take an indirect object pronoun (e.g. parler à qqn). It's important to be able to distinguish between them as their usage affects many other aspects of written French, such as verb agreements in compound tenses and the uses of other pronouns such as 'y' and 'en'. Like so many other grammar points in French, these are all interlinked and an understanding of these aids an understanding of the French grammar system as a whole. In addition, some examples of directly and indirectly transitive verbs are not what you would expect and differ from English, for example the French would say 'j'écoute la radio' or 'je cherche un livre', while we would say I listen to the radio or I look for a book.