In reply to Lisa S.
Hi Lisa - many thanks for your feedback.
We plan to write a blog post about how GOV.UK search works which should help you understand the system better. You may also be interested in reading the most recent post regarding search improvements over on the InsideGov blog: https://insidegovuk.blog.gov.uk/2014/05/12/new-search-results-page-design-unified-search/
We have many improvements planned which will improve the search experience further.
Thanks,
Ben