By default we suppose that the screening should be done against complete database (SWISSPROT + GENBANK + PDB) and the result consists on short sequence descriptions (the entry sections corresponding to ID, DE, OS ones of SWISSPROT databank).
If the query string is the line of words divided by spaces it means that every selected entry should have all this words at the text collected from ID, DE, KW, OS and OC sections (the space is equal to logical AND). The logical OR between two words (or two word groups at parenthesises) means that selected entry's ID, DE, KW, OS and OC sections should consist one of two words (or one of two word groups). The logical operator ANDNOT between two words means the presence of the first word and the absence of the second one in selected entries.
Sometimes you need to select databank entries contained the given query word in undefinite text section. At that case the word should be written as follows:
XX[query_word]