The Hungarian Rings puzzle is made up of two overlapping rings of coloured balls. In the version shown in the image, there are ten of each of the red and black balls and nine each of the blue and red balls. The aim of the puzzle is to restore the arrangement as shown in the image. You could swap over the red and black balls or swap over the blue and yellow balls and still call it solved.
The puzzle is relatively challenging. It's quite straightforward to separate the balls which aren't part of the intersection. You can shuffle around the other pieces up without messing up what you have done although you'd be quite lucky to get to the end without breaking and reforming those sets of ten. Thereafter, you need to work out a move to rearrange the balls which go in the middle (yellow and blue).