Definition
Cohorts isolate behavior by acquisition month: March buyers' repeat rates versus April's, June signups' retention curve versus May's. Aggregate dashboards blend improving and deteriorating cohorts into misleading averages.
Why it matters
Almost every 'growth slowed' mystery resolves in cohort view - either newer cohorts weaken (acquisition problem) or older ones decay faster (retention problem). Different diseases, different cures.
All glossary terms