Explanation
https://www.snowflake.com/product/architecture/
Built from the ground up for the cloud, Snowflake's unique multi-cluster shared data architecture delivers the performance, scale, elasticity, and concurrency today's organizations require.

In an auto-scaling multi-cluster virtual warehouse with the SCALING_POLICY set to ECONOMY, another cluster is started when the system has enough load for 2 minutes (A). This policy is designed to optimize the balance between performance and cost, starting additional clusters only when the sustained load justifies it2.

In Snowsight, Snowflake's web interface, user preferences can be customized to enhance the user experience.
Among these preferences, users can set a default database and default schema. These settings streamline the user experience by automatically selecting the specified database and schema when the user initiates a new session or query, reducing the need to manually specify these parameters for each operation. This feature is particularly useful for users who frequently work within a specific database or schema context.References:
Snowflake Documentation on Snowsight User Preferences

The SQL command Select * from table(validate(t1, job_id => '_last')); is used to return errors from the last executed COPY command into table t1 in the current session. It checks the results of the most recent data load operation and provides details on any errors that occurred during that process1.