MongoDB Stitch is a serverless platform that isolates complexity and 'plumbing' so developers can build applications faster. It allows for testing functions through the console or mongo shell, storing triggers in a Git repository, and integrating with various services using built-in integrations or custom implementations. MongoDB Mobile is an embedded version of the MongoDB database that provides persistent storage on devices and enables sophisticated queries and aggregations. Developers can download and embed MongoDB Mobile by adding a single line to their Android or Xcode project, and start building their first Stitch app with one of the provided tutorials.