Kellen Evan and James Rucker's tutorial outlines the process of building an application search feature using Ruby on Rails and Elastic App Search, formerly known as Swiftype App Search. The guide emphasizes the importance of a fast and efficient search experience for users, highlighting how Elastic App Search can enhance user interactions with web applications by providing powerful, intuitive search capabilities. The tutorial provides step-by-step instructions on setting up a sample search application, creating an Engine within App Search, configuring the App Search Ruby Client, and ingesting documents. It also covers schema alteration and fine-tuning search relevance. The tutorial shows how to synchronize database changes with App Search using Active Record Lifecycle Callbacks and offers guidance on using a rake task for mass data ingestion. Additionally, it demonstrates how to alter the RubyGemsController to implement a search bar and how to enhance search relevance by weighting different fields. The tutorial concludes by discussing the potential for more advanced search features, such as filtering results based on popularity, and highlights the breadth of possibilities offered by Elastic App Search for crafting engaging and efficient search experiences.