CSV (Comma Separated Files) is a format used for storing data in text files, particularly used for tabular data.
Its main feature is easy machine processing. A .csv file can be opened in many programmes, e.g. MS Excel or QGIS.
Why is this format used in the System?
Because it is a well-known and well-liked format. Exporting tabular data to CSV allows the data to be opened in a whole range of software, such as QGIS and Excel.