What is reading fluency?  Reading fluency is smooth reading that sounds like conversational speech.  It is NOT reading as fast as you can.

Why is reading fluency so important?  Readers who are fluent are better able to retain and comprehend what has been read.  A non fluent reader has to put in time and effort to decode unknown words.  Often by the time the reader has finished a sentence, he or she may not remember what they have read.  Short term memory has difficulty with fragmented information.  When the decoding process takes a lot of time, comprehension is impacted.  This is why we look so closely at reading fluency.