Apache Hive is a data warehouse infrastructure built on top of Hadoop. It allows users to query large datasets stored in Hadoop file systems using a SQL-like language called HiveQL. Hive converts queries into a series of MapReduce jobs that are executed on Hadoop. It stores table data and partitions in HDFS directories with table metadata stored separately. The Hive CLI provides an interface for users to issue HiveQL queries and manage tables, databases and partitions.