What's fluency and why is it a big deal?

Fluency is what makes reading comprehension possible! Ever listen to someone play the piano note by painful note? You listen to the whole thing and can't even recognize the tune! The same thing happens to a kid who reads slowly, word by painful word. He can't get a clue as to what the sentence is about, much less what the whole story could possibly mean. Officially, reading fluency is reading accuracy, speed, and prosody. Accuracy's pretty simple. He reads the words written on the paper correctly. No "he" for "she", no "she" for "he", no "truck" for "Jeep".
Speed is measured in how many words a child reads per minute. It's usually reported in CWPM, Correct Words Per Minute, so you get accuracy and speed in one measure. Prosody is a more subjective measure. Prosody is the ability to read with expression and timing so that the reading sounds like natural speech. Prosody makes a reader sound like he understands what he's reading. He stops at periods, takes a breath at commas. Most of the time, prosody's a terrific indicator of whether a kid is really comprehending what he's reading. If he sounds like it's making sense to him, it probably does!
Studies support the link between good reading fluency and good reading comprehension. But more importantly, to me anyway, common sense does, too! Lots of factors can influence whether a child can understand a story he reads. He may not have a basic understanding of the subject, it may cover a complex topic, or just be an entirely new idea for him. But if he can't read the words quickly and accurately, following punctuation clues to slow up or pause at certain words, he can't possible get the gist of what he's reading!