A paragraph is a piece of writing that focuses on a single theme or idea. It should be organized logically with a clear topic sentence introducing the main idea, supporting details and examples, and a concluding sentence that links to the next paragraph. When writing a paragraph, one should plan the topic sentence carefully, provide evidence to support the main point, and check that the paragraph flows logically and makes sense. Developing good paragraph structure and coherence takes practice but allows readers to easily understand the writer's key ideas.