Ask HN: (possibly silly) question about 'H1B eligible'

Greetings, fellow HNers!

There are few comments (on whoishiring threads usually) that mention 'H1B eligible'. Does it mean that only those who are already in the US on H1B are eligible? Or that an H1B sponsorship would be considered for folks who are currently located elsewhere, so that they could relocate to the US?

Am aware that it's a pretty silly question but am sure few others here too might have had this doubt, hence asking it nonetheless.

Please help me understand.

Thanks!