Sometimes conveying the meaning of an icon is hard, especially when the meaning isn't just one thing but two things. In the case of Google Events, they use an intuitive bookmark icon to let users save an upcoming concert. That's one thing - but what's the benefit or impact of saving the event in the first place? That's a challenge to get across without supplementing the experience with something else.
Several months ago, we were planning to see Luna at Lincoln Hall. After doing a search for the show, I found a list of upcoming Luna shows. We weren't sure which date would work, so we saved a few. After tapping the hollow bookmark icon, it filled with color (an ubiquitous, best practice for an on/off toggle to provide visual feedback).
But on top of that, Google displayed a snackbar (a pattern from Material Design) in the bottom right of the screen to tell us the benefit - 'You'll get reminders and updates about this event'. Finally, in the snackbar, they provided a handy navigation link to all of our saved events (Your Events).
Nice job, Google.