The "search" switch at Admin -> Settings -> Switches enables all search-related features. You normally want this on, but in some cases people want a pure directory with no search functionality. If you don't want any searching, turning off the search switch will hide all such options.

More detailed articles about doing things with the search feature:

• Searching with checkboxes
• Location filtering
• Searching by state
• Postal code range searches
• Search in forums
• Search logging
• Linking to search results
• Remote searching