What is a table format, and how does it differ from a file format?

A file format (like Parquet, ORC, or Avro) defines how data is encoded and compressed within a single physical file — how rows and columns are laid out on disk, what compression is used, how to read a specific file efficiently.

A table format sits one layer above that: it defines how a collection of many such files together constitutes one logical table — tracking which files currently belong to the table, what the table's schema and partitioning look like, and how changes to that collection of files happen safely and atomically over time.

This distinction matters because a directory full of Parquet files alone doesn't answer questions like "what is this table's current schema" or "which of these files are actually part of the current, valid version of the table" — a table format is specifically the missing layer that answers those questions reliably, which is exactly the gap Iceberg fills on top of underlying file formats like Parquet.