These are the trend bars. You'll start to see them once Life Cycle has enough data to estimate an average time spent on your activities per day, week, month and year.
It'll take a few weeks before you get your first trend bars, but after that, you're good to go. Once they show up, they display the difference in that time period's activity compared to your average, to highlight deviations that we believe might be of interest to you.
The focus is on your most common activities for that week, which for many (but far from all) is usually Home, Work and Sleep.