A flat file is a simple data storage format that organizes information in a plain text file. Each line in the file typically represents a single record, and fields within that record are separated by a specific character, such as a comma or tab. This structure makes flat files easy to read and write, but they lack the complex relationships found in databases. Flat files are commonly used for data exchange and storage due to their simplicity. They can be easily created and edited using basic text editors. However, they may not be efficient for large datasets or complex queries, which is where more advanced systems like relational databases come into play.