What are search styles?

The search style is the search style of the navigation bar search box . 

It can be set in Setup->Site Settings->Search->Search Style : Default Style/Expand current location

The default style effect is as shown below : Click the search box to pop up a pop-up search window.

The current location expansion effect is as follows : click the search box, there is no pop-up window, but the search is expanded in the original navigation bar.