public Query createQuery(String query);

Query objects are used to find entities matching certain criteria. The createQuery method creates a query using the given Java Persistence Query Language (JPQL) string. See Chapter 10, JPA Query for details.

public Query createNamedQuery(String name);

This method retrieves a query defined in metadata by name. The returned Query instance is initialized with the information declared in metadata. For more information on named queries, read Section 1.11, “ Named Queries ”.

public Query createNativeQuery(String sql);
public Query createNativeQuery(String sql, Class resultCls);
public Query createNativeQuery(String sql, String resultMapping);

Native queries are queries in the datastore's native language. For relational databases, this is the Structured Query Language (SQL). Chapter 12, SQL Queries elaborates on JPA's native query support.