What type of search bar does this theme use

Hello, I am trying to figure out what is the name of the TYPE search bar my 2020 theme is using. When I click on the icon, the bar covers the entire header, which i find very convenient. What is that type search box called?

I don’t have this on my 2023 theme site. Do you know how I can have this functionality on the 2023 theme? If you know of a tutorial, it would be of great help.

thank you in advance.

The page I need help with: [log in to see the link]