Comma Separated Value(s), also known as CSV, is a format to store structured data using text files. The CSV format is not standardized, so various implementations exist.

In 2005, the Internet Society published guidelines for creating CSV files They wrote down best practices to structure and process CSV data.

From those guidelines and giving the lack of standardization, the header line is optional in a CSV file.

When present, the header line must be the first line in the file and must contain the same number of fields as the records. Header and records lines must use the same field delimiters.

Example:

column_1, column2, column3
aaa, bbb, ccc
111, 222, 333