A flat file is a data storage format where data is stored in a single table or file, usually in a plain text format. It is a simple way of storing data without any complex relationships.
Records in flat files are straightforward, with each line of the file representing a single entry. Individual entries within flat files are separated by delimiters. Unlike relational databases, flat files do not support relationships between different data tables. Because of this, flat files are much easier to create and understand. However, flat files are unable to handle complex data, making them an unsustainable choice for organizations that deal with large amounts of data.