> ## Documentation Index
> Fetch the complete documentation index at: https://flatfileinc-feat-updatereactquickstart.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Overview

> The anatomy of Apps

## What is an App?

Listeners are the core of the Flatfile Platform. All of your configurations, from [data transformations](/plugins-docs/transform), to [custom styling](/guides/theming), to [data export](/guides/egress) are done in a Listener. They hold the logic backing your Flatfile Spaces, defining the functionality of your implementation.

Fundamentally, a Listener is a function that listens for [Events](/orchestration/events) and takes action when they occur. This means your configurations are implemented in response to events. To understand how to configure a Listener, it's important to understand the anatomy of an Event.