The casual search input allows you to search through and choose one or more concepts.
Currently, those concepts are limited to the elements you have added in the Explorer and simple search terms.
The Signals engine will use the contents of the elements you have added - the title, summary, and description - to find signals that are similar, taking into account only the most relevant results.
Note that adding a single element without any further filters will produce the same set of Signals as the Signals Feed on the Explorer's element detail view.
Adding Search Terms
You can also add search terms to the casual search input. Simply choose the according option at the bottom of the input and a tag with the search term will appear! Adding search terms to other elements will broaden the search and increase the documents in the result set.
Opening an Element
In order to see what an element is all about, you can click on the little pill representing it in the casual search. This will open it in the stack of elements.