From Paterva Wiki
A phrase in Maltego is the most powerful entity (when used with search engine transforms). This is because absolute no modifications are made to the value of the phrase when it is passed to the query. This was done to ensure that power users can add any search engine operator to it. Thus, having phrase of 'secret format:pdf site:mil' will result in a list of all PDF files with the word secret found on websites with a domain that ends in .mil. Also keep in mind that the use of quotes (") makes a huge difference to search results. A search for '"top secret"' is vastly different to a search for 'top secret'. To make the most of the phrase entity you need to know what the extra operators are. These can be found below.
Google (not officially supported)
Properties of this entity in Maltego