what camera's does magazines and ads use?

A photographer who knows how to compose a shot, make it interesting, achieve proper lighting and exposure, appropriate depth of field, and then take hundreds of shots will have a great chance of success regardless of the camera he or she uses. Furthermore, most magazine photos required extensive editing before printing on high gloss paper.

You don't need to have a full frame camera !
I've had photos published using my Nikon D80 / D5000 / and D7000.
The gloss comes from the paper , not the camera .
I've had newspaper photos published with my Nikon P600 , a bridge camera

In the days of film, they typically used medium-format cameras like a Hasselblad. These cameras produced a superior image due to their larger film size.

Today, things has changed with digital because digital renders so much more detail than film did. Modern-day fashion photographers will typically use 35mm format DSLRs such as the Nikon D4 or the Canon 5D Mark II/III. Or, if the job requires it, they will use medium format cameras like Phase One, Pentax or Hasselblad.

Pros use these specific brands and models due to the requirements of the job. Canon and Nikon offer a huge selection of lenses, along with a massive assortment of accessories and flashes, and (just as important) profession support. Sony up until last month, had no support for professional photographers. So that meant that instead of getting loaner gear while your gear was being repaired, you're stuck. And they didn't have any kind of expedited repair service like Canikon do, so you'd be out of a camera for about a month or more. This is completely unacceptable for any pro, so they have to use Canon or Nikon if they need a 35mm format camera.

Advertising photographers also use 35mm format DSLRs from Canon or Nikon. However, again, depending upon the requirements of the job, they can use either a 35mm-format Canon or Nikon; a medium-format DSLR, and even large-format film cameras. Landscape and advertising photographers are among the last to still want to use, or need to use large-format film cameras.

So there's no one camera. Any pro will have multiple cameras from multiple brands. Each designed for specific uses. It's just like how a carpenter won't have just one hammer or one kind of saw.

The camera can be anything, literally. The best photographers in that area use or aim to use medium format cameras in either film, with digital backs, or full digital systems. Most working photographers use full frame DSLRs like the Canon 1D series. I know an amateur who shoots with a Canon 5D. These are quite expensive (many thousands of dollars)

General high end digital cameras eg Phase One

Generally DSLRs, but possibly CSCs (EVILs, mirrorless), depending on the style of the individual photographer.

"Glossy finish" is on the paper. Once a photo has been taken, it can be printed on a vast range of types of paper.

they use mostly Medium format cameras such as Phase One. These are quite expensive (many thousands of dollars)

The standard is medium format but more and more are already using full-frame although you can't count out some using crop sensor bodies out there yet.

No camera will make a shot "glossy." It's all in the lighting technique, shooting technique, and post rocessing (aka. Photoshop or Lightroom). If you're talking about the actual print, it's glossy because it's printed on glossy paper.

The camera can be anything, literally. The best photographers in that area use or aim to use medium format cameras in either film, with digital backs, or full digital systems. Most working photographers use full frame DSLRs like the Canon 1D series. I know an amateur who shoots with a Canon 5D. I know another one who shoots fashion with a Canon EOS M and yet another fashion photographer with an iPhone. It's almost all in the technique, really.

Anything they like, although most probably very good ones.

Theoretically, hundreds of models representing tens of brands of cameras
might be involved in the content of one issue of a magazine.