Example: “skin” has multiple sounds to help decipher the word as spelled: “sss”, “sk”, “ih”, “nnn”, “iinn”.

Identifying some of those sounds in order helps a reader to sound out the word “skin”. After doing this a few times in a context that helps the reader confirm the meaning of the word they’ve just sounded out they’ll learn it outright.

From that point forward they can recognize “skin” on sight without requiring any context.