Explanation
https://docs.snowflake.com/en/sql-reference/external-functions.html

The purpose of an External Function in Snowflake is to call code that executes outside of the Snowflake environment. This allows Snowflake to interact with external services and leverage functionalities that are not natively available within Snowflake, such as calling APIs or running custom code hosted on cloud services3.
https://docs.snowflake.com/en/sql-reference/external-functions.html

https://docs.snowflake.com/en/user-guide/data-load-considerations-prepare.html