Numerous are the apps available for iOS to edit, type on, and highlight photos. iOS 10 has a little known ability built in to markup your photos called… Markup!
Go into Photos. Select a photo. You will see three bars with three dots/circles that initiates editing, touch it. Then you will see a circle with three dots inside it. This will bring up additional editing options. Select Markup.
By changing your selection across the bottom, you can draw on your photo – as you might want to do to draw attention to a certain part of the photo. You can also insert text – a great way to annotate or caption your photo. The built in photo app also has filters!
Play with it!