Do descriptive paragraphs even have a purpose besides getting the reader to visualize what's being described? I feel like the only idea behind those paragraphs is to get the reader to imagine whatever's being described the way the author sees it, or the way it is. I suppose the idea could be to get you to feel a certain way about the thing being described with word choice or something.

A paragraph, wherever you may find it, is descriptive in nature. It is also about one thing. So before writing the paragraph and trying to find the main idea, you should decide what you want to write about. That will be your "main idea". Once you have decided that, your paragraph will be divided into the following parts: Topic Sentence (this is where you describe what your paragraph is about: your main idea); Development of Support Sentences (these are sentences that provide details, substance and support to your main idea; Concluding Sentence (this is the sentence where you make a conclusion about your "main idea". /// Example: I will write about "online education" (that's my main idea) /// Online education has completely revolutionized education. Before education entered the internet age, learning consisted of students, a teacher and a classroom all being in the same place and at the same time. However, with today's technology students and teachers can be in different parts of the world and meet via video conferencing applications. What's more, they don't even have to meet at all. Teachers can upload a video lesson and assign a class project. Students can deliver the project when it is ready so the teacher can evaluate it. With online education, the possibilities for interaction between teachers and learners are limitless. /// MAIN IDEA: Online education has completely revolutionized education.