Toddlers go through a phase where they love pegging and posting. Balls on Pegs privides a great pegging challenge. It is fascinating to watch a young child figure out how to succeed at this. It's not as simple as it looks. Very fine movements are needed to precisely place the pegs on the four wooden vertical dowels.
Just take care to observe your child and introduce this material when they appear ready for it. Introduce it too soon and they will simply throw the balls. It's worth watching for the moment when they are ready for it, as it's great to see the child exploring and challenging themselves to peg the balls correctly.