.xlsx (Microsoft Excel Open XML Spreadsheet) The .xlsx format is the default file format for spreadsheets created in Microsoft Excel, starting with Excel 2007 and later versions. It is a part of the Office Open XML specification and utilizes XML and ZIP compression to reduce file sizes.
The .xlsx format allows for the creation of complex spreadsheets containing data, formulas, charts, pivot tables, and various formatting options. It is more efficient and secure when compared to the older .xls format, and is widely utilized in business, education, and personal data management.

The .csv (Comma-Separated Values) format is a simple text format used to represent tabular data. Each line in the file corresponds to a row in the table, with columns separated by commas. This format is widely supported by various applications, such as spreadsheet and database software. It is commonly utilized for transferring data between different programs, as well as for exporting and importing large volumes of data due to its ease of use and high compatibility.