On the Reset screen, you'll have a number of options for deleting iPhone data and settings.
Reset All Settings - This deletes all of your preference settings, returning them to the defaults. It will not erase any of your data or apps.
Erase All Content and Settings - If you want to fully delete your iPhone, this is the option to choose. When you tap this, you'll not only erase all of your preferences, you'll also delete all music, movies, apps, and other data from your phone.
Reset Network Settings - To return your wireless network settings to their factory default states, tap this.
Reset Keyboard Dictionary - Want to remove all the custom words and spellings you've added to your phone's dictionary/spellchecker? Tap this option.
Reset Home Screen Layout - To undo all of the folders and app arrangements you may have created and return your iPhone's layout to its default state, tap this.
Reset Location Warnings - Each app that uses the iPhone's GPS to be location aware asks your permission to use your location. To reset all of those warnings to their default off state, select this.