Of all the announced new features of the Nexus 5 and Android 4.4/KitKat, one of the cooler ones was a new dialer colloquially known as the "KitKat dialer." It features a revamped UI and includes the ability to search for businesses, contacts, etc. right from inside the dialer. It also features Internet-based caller ID. The name "KitKat dialer," however, is not entirely accurate.
Google Dialer (its official name) is not technically part of KitKat because it is not included in AOSP.