What is TSV?

CSV with tabs instead of commas, and the better choice more often than people realise. Tabs almost never appear inside a field, so the quoting rules that make CSV parsing miserable largely evaporate. Anything with prose, addresses or European decimals in it is safer as TSV.

What is Markdown?

Plain text with just enough punctuation to imply formatting, which is why it ended up as the default for READMEs, issues, wikis and notes. Its tables are the awkward part - a pipe-and-dash grid that's readable enough written by hand and tedious to maintain by hand.