Your iPhone's clock by default automatically syncs with your carrier's network time, which is probably what you want ninety-nine percent of the time. If you need to know the time elsewhere in the world you can simply check the Clock app's World Clock feature with a few taps. There may be times, however, when you want your iPhone's main clock to show a time other than local - maybe while you are travelling you want to know the time at home at a glance. Perhaps you are somewhere without service and your phone can't sync, or the network time is wrong for some reason.
The Shortcuts app contains a gallery of many pre-defined programs that use one or more apps to achieve a desired result. For example, the Directions to Next Event shortcut uses the Maps and Calendar apps to quickly provide you with directions to your next calendar event. Aside from the shortcuts provided in the app, there are many avid users who share their creations online in communities such as Reddit and Sharecuts.
iOS 12's Shortcuts app has hundreds of useful shortcuts meant to make a variety of different tasks easier to accomplish on your iPhone. A reboot of the old Workflow app, Shortcuts has a gallery of pre-programmed 'recipes' that are basically small programs that use one or more apps to achieve a desired result. For example the Remind me at Home shortcut will remind you of a task as soon as you get home by using location services, Maps and Reminders. You could set this up yourself as a location based reminder, but the shortcut makes it considerably quicker and easier to do.
Every photo you take with your iPhone has associated data that you can view such as the time and date, location, camera information and more. You can also add titles, descriptions and keywords to your photos which makes them a lot easier to find with the search function. While Apple is always improving its photo search function, there always seem to be photos that are missed when you search for a keyword.
Every photo you take with your iPhone has metadata attached to it - information about the photo like what camera it was taken with, the coordinates where it was taken, date, time and more. You can add data as well, including a title, description and keywords to facilitate search results. The Photos app is able to detect faces, and if there are any faces in a photo that you have assigned names to, and the app recognizes them, then those names will be in the metadata as well.