The 'Top Searches' option defines the number of entries for the table with the most often used search-terms which resulted in a visit of your homepage.
The table may be disabled by using zero. The 'Show All' checkbox allows the display of all search-terms. If enabled, a separate HTML page will be created, and a link will be added to the bottom of the 'Top Searches' table. There are a couple of conditions for this to occur. First, there must be more items than will fit in the 'Top Searches' table. Second, the listing will only show those items that are normally visible, which means it will not show any hidden items. Grouped entries will be listed first, followed by individual items. Please be aware that these pages can be quite large in size, and separate pages are generated for each month, which can consume quite a lot of disk space depending on the traffic to your site.