Sentry is an application monitoring platform that allows developers to track errors and performance data in a Django application. To add Sentry to a Django application, developers need to create a Sentry account, install the required packages, and configure the Django project to work with Sentry. The process involves setting up a virtual environment, installing packages, creating a Django project, adding an application, registering models and serializers, creating views, adding URLs, and configuring the database. Once the setup is complete, developers can test Sentry's integration by triggering errors in their code and verifying that Sentry detects and reports them correctly. Additionally, Sentry provides performance monitoring capabilities to help developers identify slow responses and long page loads, allowing them to optimize their application for better performance.