A dialer app is an application on your phone that allows you to make phone calls. It usually has a keypad interface where you can type in the phone number you want to call and then connects the call for you. Full definition
The most visible change brought by the update is the new phone dialer app which introduces a card - based interface for the favorite contacts section and a new color scheme for the phone dialer itself. (android.gs)
There was a new dialer app for vanilla Android devices that drew on the Google Maps business directory. (androidcentral.com)
You can view and manage your favorite contacts by opening the «Phone» dialer app on your iPhone and tapping the «Favorites» icon at the bottom of the screen. (howtogeek.com)