The DATEADD function in Snowflake allows users to add or subtract specific intervals from a given date or timestamp value, providing precision and ease in manipulating date and time data types. By using the function with a negative value for subtraction, users can easily perform date subtraction, such as retrieving all orders placed three days before a specific date. This powerful tool is valuable for filtering and analyzing time-based data in Snowflake's data warehouse, and users are encouraged to explore other date and time functions available in Snowflake for effective use.