Context cllues can tell you what an unknown word means or how to pronounce words that look alike.
some examples.
My favorite equine is Tagalong. I rode her yesterday. Even if you didn't know equine meant horse, the context tells you that it is something with a name that is ridden, so you would use context clues to decide that equine meant some kind of riding animal, probably horse since that is the most common.
I will read the book tomarrow.
I read the book yesterday. Based on the context you know that in the first sentance you say "reed" and in the second you say "red" even though both are spelled exactly the same.