Your Mac shows the same printer twice
It's one printer, written down twice by mistake. macOS adds a second listing when it rediscovers a printer with slightly different details — after a firmware update, a router change, or a macOS upgrade. Both point at the same machine, but usually only one has the right driver.
Why it matters
The two listings are not equal. When macOS can't match a printer to its proper driver it falls back to a general-purpose stand-in, and printing through that produces wrong colours, wrong margins, or nothing at all — for a reason you'd never guess by looking at the page.
So you can have a printer that works perfectly through one listing and badly through the other, with nothing on screen to say which is which. If your printing suddenly went wrong for no reason, this is a strong candidate.
Which one to keep
Open System Settings → Printers & Scanners and click each one. The keeper is the one whose driver names your actual printer model. The one to remove says something like Generic PostScript Printer.
Deleting a listing does nothing to the printer itself. It only removes an entry on your Mac, and you can add it back at any time.
Then make sure you're printing to the right one
Removing the bad listing isn't enough if it was the default. In the same settings panel, set "Default printer" to the one you kept — otherwise your Mac may keep choosing the wrong one in the print dialog.
Why it comes back
If the duplicate reappears, the printer is advertising itself under a changed name — often after a firmware update. Removing both listings and adding the printer once, fresh, usually settles it.