Ultimately it's ambiguous and bad. But most mathematicians (at a level higher than primary school education) use multiplication by juxtaposition—aka implicit multiplication—at a higher priority than division. BIDMAS, as you might have been taught in primary school, is an oversimplification that doesn't even account for the possibility of juxtaposition, because you didn't learn about that until secondary school.

Most mathematicians would use logic that lets you arrive at the answer of "1", while also saying it should have been written better. Brackets are cheap. Use them!

Please Excuse My Dear Aunt Sally

If you believe multiplication goes before division then 1. 8 / (2 * 4)

If you believe multiplication and division are of equal importance 16. 8 / 2 * 4

SQL, Google, and I believe C++ and HLSL would say the latter: (16)

what’s the correct one?

Yes, one is correct :-)

There's some academic debate on it, you'll hear different things. A hard interpretation of PEMDAS would say 16 is correct, however PEMDAS is fairly new and predated by algebra and implicit multiplication.

If you replace (2+2) with x:

8 / 2x = 4 / x = 4 / (2+2) = 1

Thus implicit multiplication takes priority over division. IMO, anyway.

Meanwhile:

8 / 2 * x = 4 * x = 4 * (2+2) = 16

Explicit multiplication follows PEMDAS, left to right for multiplication/division.