Notification centre, calendar, and reminder confusion

iOS & iPadOS

Hi everyone,
I have used iPhone 5 with iOs7 for six months. It's very interesting, and I can manage most of build-in apps. However, I cannot grab Notification, calendar, and reminder. And I could not find any tips on applevis, too. Please share your experiences, user guide, or podcast to me. All your helps are appreciated.
Thanks a lot