information retrieval
finds documents containing 'information' or 'retrieval'

information or retrieval
same as above

information and retrieval
finds documents containing both 'information' and 'retrieval'

information not retrieval
finds documents containing 'information' but not 'retrieval'

(information not retrieval) and WAIS
finds documents containing 'WAIS', plus 'information' but not 'retrieval'

web*
finds documents containing words starting with 'web'