They are prey to many birds and animals. The sun is too bright. They are too tired to come out. A paragraph is a group of sentences that are all about one main idea or topic. The main idea is the most important idea in the paragraph.
Most paragraphs contain a topic sentence that states the main idea.
All the other sentences in the paragraph will tell more about the main idea. Read the following paragraph about the scales on a fish. Most fish are covered by scales. Their scales form the outer protection for the fish. The scales overlap one another like tiles on a roof.