Searching a zone (e.g. Adept Illusionist) allows you to look at the cards in those zones and potentially find something. Only effects which use the word 'search' are considered to be searching a zone. If you search a public zone, then you must find what you're searching for, if possible. If you search a private zone, then you may choose to fail to find what you're searching for, even if it exists in that zone. When returning cards you have searched through to the top or bottom of a deck, specifically, you may choose the order for them. Some search effects say 'shuffle if needed.' This is usually because the effect gives you the option to search a private zone, and/or public ones. If you choose to search a private zone, you must shuffle afterward, but if you only search a public zone, you do not shuffle. For instance, if you use Adept Illusionist's ability to summon another copy from your cemetery and do not search your spellbook, you do not shuffle your spellbook.