The following are the different cases:

• Resources in the template but not in the Azure platform: Incremental deployment will create these resources on Azure and configure them according to the template-provided configuration.
• Resources in the template and also in the Azure platform: Incremental deployment will not touch these resources if the configuration matches. However, if there are configuration differences, the deployment will try to configure Azure resource with the template-provided configuration. If the configuration does not change the type, location, or any property that modifies the nature of the resource, the application of the template configuration is successful, otherwise it results in an error.
• Resources in Azure but not in the template: Incremental deployment will not touch these resources.