Thanks for asking and sorry if it is unclear -- I tried to make the titles as descriptive as possible but I appreciate the feedback. The Apple Watch measures minutes of "exercise", which it defines as activity at or above the pace of a brisk walk. This should provide a rough estimate of daily minutes of "moderate-to-vigorous physical activity", which is what is referenced in most physical activity guidelines. Each dot represents the minutes of exercise that my Apple Watch recorded on a given date.

Notably, I have not taken into account daily wear time in this figure (e.g., it is possible that changes in daily exercise are related to changes in wear time, where fewer minutes of exercise are recorded because the watch is worn for less time). I have always worn my Apple Watch consistently so this shouldn't be an issue with my data, but something to consider with wearable data in general.