Team Capacity
Two metrics describing how many people actually worked on a project or team in the selected period.
Both metrics are calculated only at the project and team level: they speak to a group of people, so they make no sense and do not appear at the level of a single participant.
Team Capacity
The number of unique, active participants in the selected period. It does not count bot accounts.
This is a count of "how many different people showed up at all", regardless of whether they worked one day or through the whole period: a person who made one commit and left counts the same as a person who worked full time throughout the whole date range. By itself it is a metric of team size, not of its stability or involvement. That is what the metric below is for.
Effective Team Capacity
How many people worked on average, on each business day of that period, not just how many people were active at all at any point. If part of the team joined or left during the period, Effective Team Capacity is lower than the raw Team Capacity: the more such changes, the bigger the difference between them.
A large difference between Team Capacity and Effective Team Capacity is a signal of high turnover or very uneven involvement in the selected period (for example, many occasional participants alongside a stable core of the team). The two numbers side by side show this faster than browsing the participant table. When the two values are close to each other, the team worked in a fairly stable, full lineup throughout the period.
This metric is also the basis for calculating the daily "per person" values for Calories, Increments and Lines: they are divided by it, not by the raw Team Capacity, to account for the team's real, time-varying composition. This way, for example, "Daily Calories / Person" does not drop artificially just because a new person joined the team halfway through the period and has not had time to do anything yet.