What is burst binding?

Burst binding is very similar to perfect binding where the spine is glued with hot glue and a cover attached. Burst binding improves on this process by perforating, fine-cutting or 'roughing' the paper spine before binding to allow greater glue penetration and thereby higher spine strength in the finished document. 

The scoring or roughing up of the spine is usually done by an attachment on a perfect binding machine - methods can vary depending on the what process you are intending to use.