My absolute favourite as a kid.
It's basically a small egg covered with milk chocolate and there's a surprise inside it, my dad used to buy this to me pretty often. I remember that everytime he returned from work he used to hide it in our house, and I had to find it if I wanted the surprise...I was 5y old and it was so much fun. I still have almost all the surprises, they're like a special memento of these funny moments. The quality of the surprises was very high back then, now I dunno what happened but atm they're just lame, I bought two eggs to my little sister a few weeks ago and I was so damn disappointed.
There's also an alternative called
Kinder Sorpresa Maxi, it's a giant version of the egg with a bigger surprise (or a lot of small ones), so basically an Easter Egg.