Answer:
We use the specific purpose to develop and organize better our speech. It represents the idea or statement which addresses our speech beyond our general purpose. In general, the focus of the specific purpose is to inform and persuade, by describing what we will actually try to achieve with our speech. It provides us the directions for our speech and describes the general purpose.
The specific purpose should answer some general questions about our speech, as, for example: what is the purpose of the speech, what are we trying to achieve with it, or what is our focus.