applies to any changes made to existing options available within the default installation of CRM, examples might include changing the default currency from USD to AUD or the way emails are sent; using the Email Router instead of Outlook etc.
Configuration applies to objects like: Business Units, Security Roles, Users, Teams, Field Security, Auditing, and SolutionsCustomization
is anything that can be done within CRM without resorting to the SDK or external code. Adding new fields to an existing entity, creating new entities, option sets, reports etc.
Customization would apply to: Fields, Entities, Relationships, Forms, Views, and Charts, Workflows, Imports etc.Extending
See the TFS
rule for correct definitions.