I have a 2004 ford ranger and I was told I need rear drum brakes and the adjuster needs to be replaced but I have no idea what they’re talking about with the adjuster

 

I would assume they mean the "star" adjuster. They get seized up with rust and gunk after a while. I usually replace all the hardware (springs etc) when I do the rear shoes but sometimes the adjuster can be cleaned up and relubed.

Here's what I'm assuming they mean: LINK

 

+1 ^^^

Good read here on Ranger Rear brake servicing: https://www.ranger-forums.com/engine...-brakes-81906/

You can see the Star Adjuster at the bottom, there is one on both sides, inside the drum, this adjusts the brake shoes out, as they wear down so they are always close to the drum for best braking

If you had an inspection "they" may think you need new brake shoes because they are worn out

But............."they" could also mean the Parking Brake adjuster, so the Parking Brake Cable adjuster is also rusted or worn out, seen here: https://i.imgur.com/pD5AcJw.jpg

This is on the drivers side, on the outside of the frame under the front of the Bed

If your Parking brake pedal goes to the floor and vehicle can still roll then that could be the problem, along with worn out shoes(brake pads)