The Gecko theme after installation has a search function in the header. In the standard configuration, this is a feature that allows you to search for WordPress content. You can enable or disable it using the settings available in the Gecko Customizer. To get to them go to WP Admin -> Gecko -> Gecko Customizer -> Theme -> Header -> Header search section.
If you are an Ultimate Bundle subscriber, you can expand its capabilities by enabling the New Search feature available through the Early Access plugin (PeepSo -> Config -> Early Access). Next:
IMPORTANT: This feature is in BETA version.