They are words that occur most frequently in all kinds of writing. Some words are important to learn because they occur in reading about special topics, such as science or social studies words. Reading important words quickly is important. Knowing words right away instead of needing to figure out words helps readers read more quickly. This is called fluency.
Greater fluency helps readers understand what is read.
Understanding what is read is the purpose for reading. Figuring out unknown words while reading. Using the Context - Use the illustrations and other words in the sentence to figure out the unknown word. Using Decoding - Use what you know about the sounds letters make to figure out the unknown word. Use what you know about prefixes, endings and syllables to figure out the unknown word.