What TXT is
Plain text here means columns lined up with spaces, the way a command line tool prints a table.
Terminal output, log files, fixed-width exports from older systems.
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 TXT to CSV
Two shapes are handled. If the same character positions are blank on every line, those gutters are treated as column boundaries, so values containing single spaces stay intact. Otherwise the lines are split on runs of whitespace.
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.
A .txt file has no internal structure to read, so the columns are inferred from the spacing. Files exported from mainframes and older reporting systems are usually fixed-width, which detects reliably. Files that are just space-separated are handled too, less reliably.
Tab-separated .txt files are a different thing again, and they detect as TSV rather than as text. That is the better outcome: a tab is unambiguous, so no guessing is involved.
Blank lines are dropped. Page headers and footers repeated through a printed report are not, so a long report may need a pass in the grid to remove them.
What carries over from TXT to CSV
CSV can express everything plain text holds about a table, so this conversion is about shape rather than loss.
plain text and CSV can express the same things about a table, so nothing is lost here - only rewritten. Columns are held apart by spacing alone, so the alignment is the structure. 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 plain text 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.