Word families are groups of words that share the same ending pattern, such as "hat", "mat", and "cat". Words in a family will always rhyme; however, not all rhyming words belong to the same word family. "Hair" and "care" both rhyme, but come from different families.
Children will need to learn to recognize the "chunks" that make up many different word patterns. For example, in the words "shake", "take", and "make", kids will learn to recognize the "ake" as a whole chunk, instead of needing to sound out the letters individually.
In kindergarten, children learned the alphabet and how to sound out words letter by letter. In first grade, they learn to see word sounds in chunks and patterned groups, so they recognize parts of the word faster and can read more fluently. In second grade, children will tackle some of the harder families of words, and the easier ones will become automatic.
Some children may have trouble perceiving or remembering word patterns and insist on sounding out every letter, every time. Others may confuse similar patterns, such as -air and -are, especially if these are taught too close together.
One common problem when moving beyond the simple decoding of words is that often there are several words in a word family that are rarely used, and children may not know what they mean. This is especially true for language learners. To learn the "-ark" family, for example, kids are taught the words: mark, bark, dark, spark, shark, lark. "Lark" is rare even for most adults (unless they are bird watchers, or enjoy cavorting on a mountaintop) and when words are meaningless to kids, learning is less secure.
Remember--every child learns differently. Doing word family activities and playing word family games are a great way to involve kids' whole bodies to reach kids of many different learning styles, and help struggling learners.
But don't put all your eggs in one basket; spend time on other reading strategies as well, and you will be likely to find the thing that most helps your child read.