It will complete any word that fits a pattern you are searching for. For example, if you are looking for a 5 letters word and know 2 of the letters, the finder will suggest all the words that fit your search – i.e. typing "h.u.." will display all words that fit this pattern – “house”, “hours” etc,

Word sources:
The MILA Hebrew Lexicon - Alon Itai and Shuly Wintner. "Language Resources for Hebrew." Language Resources and Evaluation 42(1):75-98, March 2008.