The MongoDB Stitch React Native SDK allows developers to create single apps that work on web, iOS, and Android using React Native. The SDK provides native SDKs for both iOS (Swift) and Android (Java), making it easy to connect to the Stitch app and the Atlas database. Developers can use Stitch's anonymous login feature to authenticate users and store user data in a MongoDB collection. Additionally, they can invoke Stitch Functions to retrieve personalized content, such as welcome messages, for each user.