Google Keep is an app that falls into the same category as Evernote and Apple Notes. It has recently become available for iOS. Now it is supported on Android, iOS, as a Chrome add-in and as a Web app.
These apps give you the ability to loosely organize information from different sources. You can group together web links, photos, lists, written notes, scanned pictures, etc. into categories, and to access the information from any device.
As an example, I use Evernote for my business. I keep “notebooks” in Evernote for each client. Each client notebook contains my notes from visits and calls, web links to products I may have recommended, emails we exchanged, scans of receipts,if I purchased equipment, and anything else of interest to that client. And everything is available to me on my computer, my iPad and my iPhone. I find it incredibly useful. Google Keep and Notes can be used much the same way.