Google will now give you current wait times at nearly one-million restaurants
Click on one of the bars and you'll see the estimated wait time for that particular time period. And scrolling left and right will give you a summary of each day's wait time. This can help you plan your dinner better, allowing you to beat the crowds when you reserve a table.
So you might be asking,"where does this data come from?" Similar to Google's popular times and visit duration graphs, the info comes from anonymous Google users who are willing to take the time to pass their dining experiences on to Google. Eventually, this information will also be available on Google Maps.