CSV is a file format that belongs to the category of text. Its developer is unknown, and the name is an abbreviation for Comma Separated Values. A text file in CSV format can store the data necessary for organizing tables, as well as those that can be imported into the database. This text format is intended for the presentation of tabular data and can be classified as tagged documents. The values of individual data are separated by a special symbol - a comma. However, some programs may use other characters as a delimiter.
XLSX is a more modern version of the spreadsheet format, a type of e-book within the Microsoft Office Excel suite. It takes its name from the Microsoft Excel Open XML Document. This format has replaced the XLS. Initially included in the paid package of MS Office, but then the Open XML standard was recognized as public. As in XLS, the data is placed in the cells of the table, however, it uses data compression like ZIP. This reduces file size and increases the potential for data security. Data can be entered into the cells manually, as well as by automatic calculations - when special formulas are entered into the cells, starting with the equal sign.