On the other hand, customisation is a slightly more complicated procedure and comes in where getting a specific functionality with configuration is impossible. In other words, it is a more detailed modification process and can only be done successfully by a Salesforce developer. Here possible customisations may include:
Creating custom processes, e.g., for the calculation of expected revenue/taxes
Enabling bulk operations, which imply processing large volumes of data
Enabling custom email templates created with Visualforce, for instance, for invoices and warranty emails management
In practical terms, customised Salesforce solutions usually have elements of both configuration and customisation. To achieve a better balance between the two, it is always beneficial to begin with configuration while leveraging in full the default Salesforce capabilities and tools. Once such a need arises in a Salesforce solution that cannot be addressed only through configuration, then we must utilize processes of customisation.