Presto has several important components that allow you to easily manage data. These components are catalogs, tables and schemas, and connectors. Presto accesses data via connectors; each data source is configured as a catalog, and you can query as many catalogs as you want in each query. The catalogs contain schemas and information about where data is located. Every Presto catalog is associated with a specific connector. Keep in mind that more than one catalog can use the same connector to access different instances of the same data source.
Catalogs are defined in properties files stored in the Presto configuration directory. Schema is what you use to organize your tables. Catalogues and schemas are how you define what will be queried. When addressing a table in Presto, the fully-qualified table name is always rooted in a catalog. For example, a fully-qualified table name of hive.test_data.test would refer to the test table in the test_data schema in the hive catalog.
If you run a SQL statement in Presto, you are running it against one or more catalogues. For example, you can configure a JMX catalog to provide access to JMX information via the JMX connector. Other examples of catalogs include the Hive catalog to connect to a Hive data source.
You can have as many catalogs as you need. For example, if you have additional Hive clusters, you simply add additional properties file to etc/catalog with a different name, making sure it ends in .properties. For example, if you name the property file sales.properties, Presto creates a catalog named sales using the configured connector.