A cohort is a group of users that share certain event together for a certain period of time (for example: users who make payment for the first time in the last 30 days, or added 7 friends in the last week). In other words, a cohort is a group of people with similar behavioural characteristics. Cohorts let you group your users based on their actions, such as who performed add to cart event in the last 7 days but didn’t perform checkout event. List of users who belong in a cohort is automatically kept up-to-date, and you can segment funnels, retention, user profiles, flows and drill data based on cohorts you create.

Funnels are used to track the goal completion rates of a step by step path inside your application. These goals (steps) are defined as custom events in Countly and you don't need any extra/new API calls if you have already been using custom events. Countly Drill is advanced segmentation feature, available with Enterprise Edition. Drill can be very powerful when it comes to understanding segmented data. This video provides more information and shows how to use Countly Funnels and Drill.