What is TSV?
TSV is CSV with tabs, and the swap removes CSV's worst habit: prose is full of commas and almost never contains a tab, so fields rarely need quoting at all. It is what you want when the data is text-heavy and the quoting keeps going wrong.
What is CSV?
CSV is the least glamorous and most durable data format there is - rows of values separated by commas, readable by every spreadsheet and database ever written. Its subtleties are all about quoting: a value containing a comma has to be wrapped, and a quote inside that has to be doubled.