Experiments Graph Overview
The graph itself is simple and shows each layout experiment in a different color. The more a color is shown, the more users are seeing it. This is for a site's optimization over almost a year, which is why it looks like a lot to take in. You can toggle between screen sizes - by clicking on the desktop / tablet / mobile button and change the date range too.
Going back in time to when this site went live. As you can see from the graph - the system has split the traffic between 5 main layout tests for desktop, together with a number of smaller tests. After gaining enough data (in this case, after a month of testing) a 'winner' (Experiment Oilfish, shown in light blue) was 'promoted'. When a site has a 'winner', the system sends it more traffic so it can begin to improve the income and UX overall. The remaining traffic is for more testing - and finding new winners over time.