Vijay Umapathy, writing for the Official Gmail Blog:

Our calendars should help us make the most of our time — scheduling meetings at work, remembering brunch with friends, and keeping track of all our other commitments. But often our to-do list is elsewhere, separate from the Calendar that organizes our day, and we end up overcommitted or miss something important because we forgot to check our list.
Now there’s a single way to manage your day: starting this week, you can create Reminders in Google Calendar to keep track of your to-dos alongside your scheduled events.

Reminders aren’t just kept in Google Calendar either, they will also be accessible from the Google Inbox, Google Keep and Google Now apps - and they’ll be coming to the web in the future. For those of you invested in the Google ecosystem, and just need a simple way to remember about tasks you need to do, this new Reminders feature from Google may be a perfect fit.