Snowflake stores a table's underlying data using a columnar file format and micro-partitions. The columnar file format ensures efficient storage and retrieval by storing data in columns rather than rows, which enhances query performance. Micro-partitions allow Snowflake to divide data into smaller, manageable chunks, optimizing storage and enabling parallel processing for faster query execution. This combination of columnar file format and micro-partitions is foundational to how Snowflake manages and processes data efficiently.