There is a significant difference between an essay and a paragraph. A paragraph is generally fairly short. It should have a specific topic or theme. The body of the paragraph should explain the main point or idea of the paragraph. In a paragraph, there is a topic sentence, followed by supporting details, and a conclusion.
An essay consists of several paragraphs covering the main idea or thesis of the essay. Writing an essay generally requires more time, thinking, and preparation. More research often needs to be done to develop the main idea of an essay.
Most students are familiar with a five-paragraph essay. The first paragraph introduces the main idea of the essay. The next three paragraphs are used to support the main idea. The last paragraph summarizes the main concept of the essay. It should support the main idea made throughout the essay.