Definitions

Active person
Someone who completed a module, instant module, quiz or survey in the period. The base for everything else.
Reach
Of active people, the share who touched the feature. Same base for every feature.
Depth
What someone did once they arrived: completions per person, time, scores, actions.
Return
Weekly: share of a week's active people who were also active the week before. Monthly: same, by month.
Split by company
Every number can be filtered by company. "All" shows the largest companies as separate lines.
Active admin
Hub user who did something beyond viewing: created, edited, published, exported, and so on.