Files in CSV (comma-separted values) format contain tabular data, with one row per line and columns separated by a comma (
There are many CSV variants, having to do with whether and how fields are quoted and may or may not include commas and newlines.
Sometimes files with tabular data are called CSV even if the separator is not a comma (semicolons and tabs are commonly used).
Simple tools like awk are suitable for CSV files without quotes. For files with quotes around fields, use a proper CSV parser and tell it what quoting rules the file uses — see Is there a robust command line tool for processing csv files?