Hi. Unfortunately, you didn't deliver the talk this question refers to. This makes it impossible for it to be answered accurately. However, I will try to help you as best I can.
To find the areas where the talk fits, you will need to read or listen to the talk and identify those areas in the speaker's speech. These areas refer to the type of subject that the lecture addresses and the direction of the lecture and relation to the themes and objectives it wants to achieve.
Regarding the difference between the spoken language and reading, we can say that the spoken language requires that the individuals involved have the skills to speak coherently and to listen efficiently. These skills, however, are not necessary in reading, where individuals need to display skills in interpretation, reading, writing and concentration.