Question: I am wondering about the differences. Based on my understanding, MLP is one kind of neural networks, where the activation function is sigmoid, and error term is cross-entropy(logistics) error. Looking for help, thanks!

Answer: 
MLP is fully connected feed-forward network. In particular CNN which is partially connected, RNN which has feedback loop are not MLPs.
The main difference is that MLP is one way. Thus, it's a feedforward network without any loop. Whereas, Neural networks such as DNN can contain loops. See more [here](https://www.kaggle.com/getting-started/46727)