This is not strictly speaking a plugin, but rather a module created in the NatSci theme for Mura. It is a display object, so it can be dragged anywhere in a page during inline edit.
The form simply include a title, a search box and a button. The title can be customized in the parameters, as well as the "placeholder" text displayed in gray in the search box before users type something.
Search results are be displayed on the same page (replacing its contents).
It is possible to set the search to work for the entire site, but this would be redundant with the top-right search box in the NatSci theme, which is part of MSU web standards.