"You might already create calendar entries to remind you to call the doctor or pick up groceries on the way home. But while those entries come and go, Reminders stick with you over time so you can track them until they are actually done. If a Reminder isn't completed, it will appear at the top of your Calendar the next day. And the next. When you do finally call the doctor or pick up those necessities, just swipe the Reminder away ... and you're onto the next to-do," informs Google.
Calendar events are different from reminders, but you can now manage them from the same app. Google promises to bring this feature to the Google Calendar web app in the near future.