The spellchecker capability is an advanced feature of search engines that allows returning of correct suggestions even if queries are misspelt.
Today most web users are familiar with the “Did you mean… ?” feature that suggests search terms for queries with spelling errors.
This feature is particularly useful for queries with 0 results and those with few results; in fact, using terms from your index or an external dictionary to make suggestions and always return relevant results can have a major impact on meeting user needs and sales (in the case of e-commerce).