A CSV file is a text file in which the values are separated by commas.
For example, you can "Download As > Comma-separated values (.csv)" in Google Drive (Sheets).
You can also upload an Excel file to Google Drive, and download it as a .csv file from there.
Important Note: If the file includes any characters outside the normal ANSII character set (see examples below), then it must be correctly encoded as UTF-8, so we recommend using Google Drive – see above.
Excel does not have an option to save a .csv file encoded as UTF-8; that is, as Unicode text.
International characters: Accented characters, e.g. à, á, â, ã, ä, å, etc.
Multibyte character sets: Arabic, Chinese, Greek, Hebrew, Hindi, Japanese, Russian, etc.