Settings
The Search action turns your form into a search form. It has a single setting, Search phrase, which is the text to search your site for. On submit, the visitor is taken to your site’s normal search results page for that phrase, using the same results page and permalink settings as WordPress’s built-in search.
In practice you set the Search phrase to the value of a search input on your form, using a dynamic variable, so it searches for whatever the visitor typed. Like a redirect, a search takes the visitor to the results page instead of showing the success screen.