Just like the name says :

I got a mixture of these candy bars recently, milk and dark. One type had a "meltaway center" (The milk chocolate), while the other type didn't (Dark). When I saw that description of the special core on the milk chocolate bar, it made me more drawn to it. I didn't know what this would feel like on my tongue, but it sounded heavenly. I loved the sensation; it was extra smooth, chilly and the candy's center disintegrated at an accelerated rate. I preferred the milk chocolate to the dark chocolate. It was more mild and I liked that it had the meltaway middle. Both of them were sweet and the dark chocolate wasn't bitter, but I enjoyed the milk chocolate better. It's a personal preference. I think people would enjoy either. The rich, dark chocolate has a regular center. When you eat it, it is firm and is solid the whole way through. Each Bliss bar is one long piece that can broken into 5 smaller, bite-size squares. So yummy.