The iOS and Android mobile apps for Google Calendar are both getting a new feature this week. When new versions of the app hit the iTunes App Store and the Google Play Store, respectively, Calendar will have support for reminders. These will reportedly come to the Web version of Google Calendar too, at some point in the future.
Reminders help you keep track of your to-dos alongside your scheduled events (which have lived in Calendar so far). While events are tied to certain dates and times, reminders "stick with you over time so you can track them until they are actually done", Google says. If a reminder isn't completed, it will show up at the top of your calendar the next day - and the next after that, and so on. So you clearly won't be able to miss anything on your to-do list from now on.
When you are finally done with a reminder, you just swipe it away to the side and it's gone. Reminders are more useful than events because for them Google Calendar automatically adds stuff such as phone numbers and addresses. So a reminder telling you to call someone or run an errand will display the phone number or address within easy reach. Calendar uses information from your contacts along with Google's knowledge graph to power this feature.
Reminders can be created from Inbox, Keep, and Google Now too. And they will all show up in Calendar immediately.