The ARFF (Attribute-Relation File Format) is a text file format developed by the Machine Learning Group at the University of Waikato for describing datasets used in machine learning. It is primarily used with the WEKA (Waikato Environment for Knowledge Analysis) software, but is also supported by other machine learning tools. An ARFF file consists of a header section and a data section. The header section defines the relation name (dataset name) and the attributes (features or columns) of the data. Each attribute is declared with its name and data type (e.g., numeric, nominal, string, date). The data section contains the actual data instances, with each instance represented as a comma-separated list of attribute values. Missing values are typically represented by a question mark (?). ARFF files are designed to be human-readable and easily parsed by machine learning algorithms, making them a popular choice for storing and exchanging datasets in the machine learning community. The format supports various data types and allows for the representation of both numerical and categorical data, making it versatile for a wide range of machine learning tasks.