What it teaches
Hearing that two words end with the same sound. Rhyme is one of the strongest single predictors of how easily a child learns to read, because a child who hears -at in cat can read hat, mat and sat without being taught any of them.
What to look for
Say both words out loud. Rhyme is a sound, and a child who is reading the words rather than hearing them will be caught out by pairs like through and though.