Sometimes the same letters can make several different sounds. Listen to the sounds made by the letters 'ea' in these words.

peach

feather

steak

Now listen to the sounds made by the letters 'ou' in these words.

cloud

soup

boulder

If you know that the same letters can make different sounds it helps you with your reading. When you come across a new word you can try out the different sounds and see which one makes sense.