Couchbase Server provides different ways for applications to access data, including basic key-value operations, secondary indexes, and full-text search, each suited for specific scenarios. Secondary indexes, defined using JavaScript views with map and optional reduce functions, are ideal for quick key-based lookups and range queries, such as listing product names in a catalog. They use a B-tree data structure and offer eventual consistency with the stored documents. In contrast, full-text search is suitable for searching large volumes of textual data, as it maps document terms to document IDs, enabling efficient ad-hoc queries across the dataset. Couchbase integrates with Elasticsearch for real-time document replication and full-text indexing, allowing keyword-based searches, such as finding products with attributes like "red." While full-text search is recommended for term-based search and human consumption, secondary indexes are better for machine/programmatic consumption.