What TSV is
TSV is CSV with tabs instead of commas. Because tabs almost never appear inside a value, quoting is rarely needed and the files are easier to read by eye.
Bioinformatics, log processing, and anyone who has copied a block of cells out of a spreadsheet: the clipboard format is TSV.
What CSV is
CSV is a text file where each line is a row and commas separate the fields. There is no type system, no formatting and no second sheet. Every value is text until something downstream decides otherwise.
Almost every database, analytics tool and spreadsheet can read and write it, which is why exports default to it.
What changes when you convert TSV to CSV
The tab is unambiguous, so there is no delimiter to guess. This is the most reliable of the delimited formats to read.
Any value containing the delimiter, a quote or a line break gets wrapped in quotes, and embedded quotes are doubled. That is the rule in RFC 4180 and it is what spreadsheet software expects.
What carries over from TSV to CSV
CSV can express everything TSV holds about a table, so this conversion is about shape rather than loss.
TSV and CSV can express the same things about a table, so nothing is lost here - only rewritten. TSV separates columns with tabs and agrees on no quoting convention, so a tab or a newline inside a value has no safe representation. Every value is text; whether the first row is a header is a convention, not part of the format.
That makes this a change of notation rather than of content: the same values, the same columns, the same order, written with the markers CSV expects instead of the ones TSV uses.
The identifier 007 comes out of the CSV as 007. Reading it as a number would have made it 7, and an id that changes value is worse than one that stays text.
The role "Analyst, data" survives with its comma, in one cell rather than split across two. That is the first thing to check in any converted table, and the usual place a CSV file goes wrong.
The quotes around Jonah "Jo" Pryce are doubled, which is how the delimited formats escape a quote in the CSV.