Which type of WSDL is tied to a specific configuration of Salesforce?

The Enterprise WSDL is specifically designed for Salesforce organizations and is tightly coupled to the individual configuration of that organization. This WSDL provides an interface that is tailored to the specific objects and fields that exist in a particular org. Therefore, if any changes are made to the data model, such as adding new custom fields or objects, the Enterprise WSDL must be regenerated to reflect those changes.

Using the Enterprise WSDL allows developers to access only the resources defined in their specific Salesforce instance, which enhances security and reduces the likelihood of issues stemming from accessing incorrect or non-existent fields or objects.

In contrast, the Partner WSDL is designed for use with multiple Salesforce organizations and offers a more generic view of the available objects. It’s useful for external applications that need to connect to multiple Salesforce orgs without being dependent on their unique configurations. Custom WSDLs are user-defined and aren't inherently linked to the specific configuration of Salesforce. Apex WSDL relates specifically to web services created within Apex code, rather than the overall Salesforce configuration.