When we read essays and speeches, we need to be aware of why the text was written as well as its message. The "why" is called

Author's Purpose.

Explanation:

A text is always written with an intention which may be either personal, social, political, etc. either to amuse the readers or to inform them or to satirize an issue. Thus, while reading a text the readers must have a fair idea about the context, the author's purpose and the message inherent as these are the most significant things to consider for better clarity of the themes and understanding of the text. Knowing the author's purpose would also assist in inter-textual, critical or comparative studies. It enlaces the reader with the lenses of the author's perception to look at the text and motivate and inspire themselves. Yet one should not get over-obsessed with the author's purpose as it may confine or restrict their thinking ability.

The why is called the Purpose