When you search, you will get a set of links to files, together with a 'rank' for each one. What you are searching for is referred to as the key. The higher the rank, the more times the key was found, relative to the length of the document.
On the website, we have pdf files for each individual discourse as well as for each volume (which contains many discourses). Suppose we search for "Mueller". It is found in chapter 23 of volume 20, with rank 176. So, this entry appears first in the list of results. Near the end of the list is an entry for the complete volume 20, since "Mueller" appears in it. But the rank is only 1 because the ratio of (the number of times "Mueller" appears) to the length of the volume is so small.
Thus, you probably want to look only at the entries for chapters rather than the entries for volumes; the volumes take a long time to download.
Examples of key word search:
'Sai Baba'
'Sathya Sai Baba'
'love'
Examples of search query:
'love AND devotion'
'love AND NOT hate'
'vegetarian OR meat OR food'
'(devotion OR love) AND NOT hate'