Support.Apple.com is where you can start.
iPhone helpful links, by Apple.
Switching from An Android? Congratulations! Move all your data using Apple's free Move app.
Get to know your iPad, resources provided by Apple.
iPad tips, by Apple.
iPad User Guide, by Apple.
Some useful tips
Did you accidentally delete calendars, or contacts, or reminders, or bookmarks? You can restore them from iCloud. This is a great tip. And it shows yet another reason why you should use iCloud.
How to View, change, or cancel your subscriptions, from a Mac or iOS. This article shows how to manage those billed through Apple or billed though others.