Upper/lower case doesn´t affect the search.
Shall several words being used and seperated using spaces, only textes are being found which contains all of these words. A word will be found, when all characters have been found in various position but in series. Optional OR can be placed before a word. If all words shall be found AND must be used in front of the words. If NOT is used in front of a word, only hits without this word shall appear.
All 3 above described combinations needs to be used upper case else they are interpreted as search items.