what is the name of the app that you talk too

Have a wee read of the manual here:

http://support.apple.com/manuals/iphone/

All will be in there

Siri is only on the iPhone 4s, it's built in-nothing to download.

http://www.apple.com/iphone/features/siri-faq.html

If you have an iPhone 4, look at the dragon apps in the app store.

FaceTime is explained here:

http://support.apple.com/kb/HT4319

If you have an iPhone 4S, it is Siri. You can access it by double-tapping the home button (the one with the square). If you have an iPhone 4, it is called Voice Control. You can do this by holding the home button.

Isla Sornia wrote:

If you have an iPhone 4S, it is Siri. You can access it by double-tapping the home button (the one with the square).

Double tapping leads to the tray with the background apps.