Please shed some light on the differences between talmud and mishnah. If both are oral torah or exegesis of oral torah why there are two?

According to the Jews, the Torah was revealed to Moses on mount Sinai, along with it he was also given the oral Torah i.e. the Talmud, which is the explanation or the commentary of the written Torah.

In the second century, these laws (i.e. the oral Torah) were finally written; the document came to be known as the Mishnah.