Read WordPress full-screen search overlay plugin for more information.
A full-screen search overlay is a good way to focus the user on specific content. Essentially, users will see a single page centered around the search field and is often considered aesthetically pleasing.
While it may not improve the website’s ability to actually conduct searches for content, it does provide a nice look and feel to how the website behaves. It may be an excellent method to separate your site from the countless others on the Internet. However, the plugin that is suggested in this post will not only give the search overlay but also will improve the search performance considerably.