iPhone offers 9 filters that you can alter your photos with - Vivid, Vivid Warm, Vivid Cool, Dramatic, Dramatic Warm, Dramatic Cool, Mono, Silvertone and Noir. You can also tweak each one's intensity on a 0 to 100 scale, so you have quite a range of possibilities when you go to post-process your photos. While this may be enough for most people, if you are really into tweaking colors and textures in your photos, which is an art in itself, then the default array of filters probably seems a bit limited.
iOS allows you to assign names to people in your photos, which the app can then use to group all pictures of that person into one album. The Photos app even has a default People folder to hold all of your individual people albums. But what if you want to group all photos of an object into an album? Maybe you want an album of all of your photos of cars or dogs. You can actually do this quite easily in most cases, or at least get a good start on it.
You may have photos in your camera roll that you would rather others not see, because they are simply private - whether they are embarrassing, compromising, have private data like passwords in them or otherwise. You probably want to keep them out of sight of somebody who might be browsing your camera roll, whether it is someone who stole your phone or simply a friend you handed it to to check out some pics. iOS offers a way to hide photos but surprisingly doesn't let you put them in a password protected album.
Having a Christmas card made with your family photos on it used to be a chore before the age of digital photography. Now you can take a few photos with your iPhone and use any one of the many photo publishing apps out there to arrange them on a card, add some decor and a message and have them mailed to friends and family. You can do this in just a few minutes right from your iPhone.
Live Photos capture 1.5 seconds of video before and after your shot, giving your photos an extra dimension of life as compared to a still. While you can trim and edit Live Photos and add effects like Loop, Bounce and Long Exposure and even convert them GIFs (with third-party apps), there hasn't been a way to convert them to regular videos, until now.