Fracture Reduction means realignment of bone fracture ends to anatomical pre injury positions. When a bone breaks the two ends often move past or away from each other. This is because of the force that caused the damage pushes the bones around.
While you're lying down, your bone doctor will stand at one end of the broken bone and an assistant at the other. They will then pull in a straight line until they feel the bones snap back in place or can see that the protruding bone ends have flattened. Of course, you'll be sedated by IV meds during this painful procedure.
Once the doctor is happy with the alignment of your bone, they'll then wrap a cast around it to hold it in place and send you for a repeat Xray to compare with the first one to make sure the ends are holding. Once s/he's happy, you're sent home and follow up arranged with a fracture clinic.