Binary hashing - what is it?

I am trying to understand what Binary hashing is. My understanding, is that you split your message into four parts, D1-D4, you then has each of those parts individually and get H1-H4. You then hash H1+H2 and H3+H4 to create H5 and H6. You then hash H5 and H6 to generate your final hash value, H. Is this correct? If not please tell me where I'm going wrong, thank you!