Is this a framing nailer or a brad nailer?

It is listed as a 21-degree full round head framing nailer, which is the structural format. The brad nailer label in the specs does not fit that, so confirm the nail range with the seller before buying.

What nails does it take?

It takes 21-degree full round head framing nails. The listing does not state a nail length range, so check that before you buy a box.

Do I need a compressor?

Yes. It is pneumatic, so it needs an air compressor and hose. Match the compressor's CFM and pressure to the nailer's requirements, which are not listed here.

Can I adjust how deep the nails sit?

Yes. It has a depth adjustment, so you can set nails flush or countersunk to suit the material.

Is it worth it over a cordless framing nailer?

A pneumatic nailer is usually cheaper and lighter and runs all day if you have air on site. A cordless model costs more but works without a compressor, so it depends on your setup.