Briefly, the state of Alaska owns the oilfields in Alaska and makes money from selling the oil. That money is then partially disbursed to people living in the state.

The actual payment has varied over time (with oil prices, mostly), peaking at $3269/person/year in 2008 but was only $878/person/year in 2012.

https://www.opendemocracy.net/en/opendemocracyuk/alaska-mode...

[former Alaska resident]

Possibly a simplified answer, but the way I understand it is that the citizens own the oil rights, and get a cut.

That’s way it’s funded just Norway funds their social programs from oil revenues and tosses the extra in their sovereign wealth fund like Saudi Arabia. Alaska is listed on the wiki page for basic income.

Small population and they sell oil.

Oil revenue. It's not enough to live on, though.