search items that include all the terms defined to be searched. For example, key in "acme AND california" or "acme + california", the results will be all the items that include both "acme" and "california".
OR(||)：
search items that include at least one of the terms defined to be searched. For example, key in "acme OR california" or "acme || california", the results will be all the items that include the term "acme" or "california" or both.
AND NOT(+!)：
search items that do not include the terms defined to be searched. For example, key in "acme AND NOT california" or "acme +! california", the results will be all the items that include the term "acme" but do not include the term "california".
