Class names could have lowercase letters, underscores, and numbers. Class names should always start with a lowercase letter. The Scope Resolution Operator (“::”) is the namespace separator for class names. The characters allowed in the case of Class names are also applicable in the case of defining module names.
The rules are also applicable to the definition of resource types and parameters. However, modules and parameters cannot apply the namespace operator. Variables or identifiers are also subject to certain rules for permitted characters. Variable names are case-sensitive and could include underscores as well as alphanumeric characters.