What is binding?
Website binding is what bridges the CMS (Portal) with the information defined in the License Manager for a specific account name.
That is, it sets that an account name (configured in the License Manager module) is linked to the folder and files structure of a particular Website (defined in the CMS module).
This is the setting made when an account wants to have more than one store. For each of these stores (which we call multistores), you make a binding.