Algolia is a performant search engine that exposes an API to perform search and discovery on data, allowing developers to create search indexes and manage data-fetching logic in their applications. The tutorial covers the process of integrating Algolia with Contentful, a headless CMS, to sync data from Contentful to Algolia's index and enable fast search functionality. By following the steps outlined in the tutorial, developers can build a Contentful-Algolia integration that keeps their index updated with data served from Contentful and enables fast filtering and searching of the data. The tutorial also introduces features such as facets, which allow developers to add categorization to their search results using attributes from their data.