Will resetting my iPhone remove all my details?

Basically I'm going to be selling my phone. If I go into 'settings' 'General' and then 'reset', will all my passwords and apps etc be cleared?

There are multiple reset choices after you click reset:

Reset All Settings - Removes all of your preferences for Wi-Fi, Bluetooth, Do No Disturb, Notifications, General, Sounds, Brightness & Wallpaper and Privacy.

Erase All Content and Settings - This will erase everything on your iPhone or iPad. So not only does this reset settings, it deletes media. Photos, music, email, videos and even your apps.

Reset Network Settings - Simply resets your Network settings, don't really need to explain that one

Reset Keyboard Dictionary - resets the auto correct and custom dictionary on your device

Reset Home Screen Layout - This will reset the home screen to the default grouping of apps, if you moved any apps around then it will move them back to how it was before

Reset Location & Privacy - This will reset location and privacy settings to the factory default setting. You want to erase all content and settings, that wipes it clean. Make sure you put in your icloud ID and password at that point, so its removed also, then its not icloud locked anymore and someone else can set it up as their own. Yes it will completely erase all data from your phone, call number, apps, saved file on phone. In case you need to have a good and advanced security app do install Leo Privacy Guard to make it utmost secure.

You want to erase all content and settings, that wipes it clean. Make sure you put in your icloud ID and password at that point, so its removed also, then its not icloud locked anymore and someone else can set it up as their own.

Yes it will completely erase all data from your phone, call number, apps, saved file on phone. In case you need to have a good and advanced security app do install Leo Privacy Guard to make it utmost secure.