# Core Concepts

- [Events](/core-concepts-1/events.md): Every time an action happens that you wish to keep track of, you send an Event to Growlytics. Events can be as easy as choosing the text string that defines them.
- [Sessions](/core-concepts-1/sessions.md): User Sessions are series of events that are performed within a single visit or interaction with your application.
- [User/Customer Profile](/core-concepts-1/user-customer-profile.md): Growlytics creates a customer profile for each person who launches your app or visits your website.