The Sentiment Analysis App is a web application built using Django and Python, utilizing the Twinword Sentiment Analysis API to analyze text sentiment. To build this app, users must create a RapidAPI user account, subscribe to the Sentiment Analysis API, and obtain an API key. The app features a form for users to submit reviews with their sentiment scores calculated by the API. Reviews are stored in a database and sorted by sentiment score, with critical reviews highlighted in red. The app demonstrates how to integrate a third-party API into a Django application using Python.