There are a few operators that you can use to refine your searches (note that these operators must be in uppercase to not be considered search terms):
error maryis the same as
error AND mary.
error OR marymeans "find any event that contains either word".
error NOT marywould find events that contain
errorbut do not contain
"Out of this world"will find this exact sequence of words.
Out of this worldwould find any event that contains all of these words, but not necessarily in that order.