What do these traffic signs indicate?

You correctly identified the sign as the indication of the start of a no-overtaking area 200 meters ahead. This sign consists of a red circle with two cars side by side, one in red and one in black, which means overtaking is prohibited. The additional plate with "200 m" below it shows that this restriction will begin after 200 meters, not immediately. It warns drivers to prepare to comply with the no-overtaking rule once they reach that distance. This helps improve safety by giving advance notice before the actual restriction zone starts.