Here's the problem. In English we use 26 symbols (the alphabetic letters) to represent 44 sounds. This means some letters have more than one sound, like the letter y (which has 3 sounds). Some sounds are represented by teams of letters. Some teams of letters have more than one sound. Think of /ow/ as in cow and snow. Some groups of letters sound the same. Think of the four letter combinations that make the same /sh/ sound: sh, ci, ti, and is.
Now imagine being 44 years old and you are learning the sound-symbols relationships. You may remember some of it from school but it is a daunting task. You may be an ESL learner who knows another alphabetic system altogether (think Arabic or an ideographic language). Reading - You Can Do It Too! gives tutors and students tools to learn alphabetic awareness and remember it.