1. Variables are considered “not found” when the code attempts to access them, but they haven’t been defined in the current scope. This includes both variables that have not been instantiated and those that are out of scope.

2. VariableNotFoundError is commonly used within the automata framework where dynamic execution of user-written or auto-generated code takes place. It often occurs in scenarios where the system needs to access a variable for a certain operation (either for calculation, modification, or returning data), but it does not exist in the current context or execution environment.

3. When a VariableNotFoundError is thrown, error handling strategies highly depend on the specific implementation and how these exceptions are handled in that context. General approaches include defining a fallback or default value for the variable, prompting the user to define the variable if possible, or simply logging the error for debugging. However, it is usually best to avoid these errors in the first place by ensuring that all variables are appropriately initialized and made available in the correct context before they are used. This could involve systematic code verification and testing procedures.