Final answer:
The CSV (Comma-Separated Values) file type is used to store tabular data with fields separated by commas.
Step-by-step explanation:
The file type that stores tabular data and uses fields separated by commas is the CSV (Comma-Separated Values) file. This format is widely used for importing and exporting spreadsheet or database information where each line in the file corresponds to a row in the table, and each field in that row (or cell) is separated by a comma. Other file types mentioned, such as PDF, TXT, and JPEG, do not typically store data in a structured table format using comma separation.