After loading data in Druid, you can run queries against the data using Druid SQL or Druid's native query language. The Druid console provides a visual interface for building and running queries against your data.
Keep in mind that users can query datasources in Pivot as well. The Druid console interface is intended to be used by data set owners or administrators to inspect, validate, and troubleshoot data ingestion and data management issues. On the other hand, data scientists and analysts would likely use Pivot to run queries and explore data. For information about Pivot queries, see SQL in Pivot.
About querying Druid data
Using Druid SQL enables you to use a familiar language for querying data in Druid as you would for other types of databases and data stores. While Druid SQL matches many features of standard SQL, it represents a subset of the functionality of Druid's native query language. In fact, Druid translates SQL queries into native query format behind the scenes.
Which to use? If you are familiar with SQL, it makes sense to start with Druid SQL. Eventually, if additional querying features become necessary or in certain troubleshooting scenarios, familiarity with native queries may become necessary.
If you are new to the Druid console and querying data in Druid, a good place to start is with the Querying data tutorial.
For extensive information about Druid SQL, see Druid SQL.