One checks spelling, grammar, etc. One gives copy overview, places it in paper. A little of both. One of our three is a seasoned journalist who truly likes looking at the copy. Very much so.
Copy editors work closely with the reporters.
Since we're a small paper, everyone usually ends up assisting with everything. Flexible time, like coming in an hour earlier or leaving a couple of hours earlier is a perk. They will probably move up to full editing slots. First editor to look over copy is extremely knowledgeable aobut the area - names, places, etc. This is extremely helpful.