how does the search icon work?

how does the search icon work?

i am trying your free trial out, and i have uploaded 4 CVs so far. However when i search key words that all 4 CVs should have.... only 2 or 3 come out depending on the word. Where and how does your search work? where should have my "key" words for me to know that all my relevant CVs pop up when i search for them.