What does sight words mean?

Sight words, i.e., high frequency words, are the most commonly used words (making up about 50-75% of words in beginning reading materials) that readers are taught to memorize by sight so they can instantly recognize the words when seen in print without trying to use other decoding strategies. Since many sight words can’t be sounded out with phonics or have unusual spelling patterns, teaching recognition of these words increases reading fluency and comprehension. There are many different sight word lists broken into levels with overlapping words and vary according to geographical location, empirical data, samples used, and year of publication.