Text files containing simple comma separated values. Use this for data that is a subset of real CSV without newlines in (quoted) field content, that can be handled with line oriented tools without the need for a real parser.
CSV files come in many varieties and don't have to be comma separated. A full-fledged CSV file cannot be handled with simplistic approach with line oriented tools as rows span multiple lines.
If data is simplified CSV, at the minimum no newlines should be included in row content and it might not have any quoted data at all (e.g. if the separator character is not included in any of the cell contents).
Describe the exact content (separator value, quotes or not possible cell content) as a few example lines don't say anything about the next line in a file.
Common tools for simplified CSV are
For real, non-subset, CSV data a parser is needed. Questions relating to that (and only those) should use the csv tag. See Is there a robust command line tool for processing csv files?