A
It's the phone app. The standard name for a phone app is "dialer". (App files are named backwards from the way you're used to seeing addresses in a web browser, so it's the dialer, for android, supplied by Samsung, or "dialer.android.samsung". All the apps that start with "com" are the same - that's the .com part that's at the beginning (instead of the end). sec is another app prefix - it would have something to do with security. Don't ever delete (if you even can) com. or sec. files. You'll break something if you do.