What Plain Text 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 HTML is
An HTML table is a table element containing thead and tbody, with th cells for headers and td cells for data.
Web pages, email templates and anything pasted into a CMS.
What changes when you convert Plain Text to HTML
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.
Semantic markup: a real thead, a real tbody, th for the header row. Angle brackets and ampersands in your data are escaped, so a value like <script> is written safely and shows as text on the page.
What carries over from Plain Text to HTML
HTML can express everything plain text holds about a table, so this conversion is about shape rather than loss.
HTML marks its header cells differently from its data cells, so the first row is written with that marker.
The identifier 007 comes out of the HTML 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 HTML file goes wrong.
The quotes around Jonah "Jo" Pryce are written as the HTML entity " in the HTML.