Code Smells refer to indications in the source code that something might be wrong or poorly designed. These aren’t outright bugs or errors but rather structural issues that can lead to problems in the future if not addressed. Identifying and fixing code smells is a crucial part of maintaining clean, maintainable, and scalable codebases.

Characteristics of Code Smells:
1. Subtle Issues: Code smells are often not immediately apparent, requiring a deeper understanding of best practices and design principles to recognize them.
2. Impact on Maintainability: While they don’t necessarily prevent the program from functioning, they make the code harder to understand, maintain, and extend.
3. Indicators of Technical Debt: Code smells are often a sign of shortcuts or rushed development, leading to accumulated technical debt.

Common Types of Code Smells:

1. Duplicated Code: Similar or identical code appears in multiple places, making updates more error-prone.
2. Long Method: Methods that are excessively long and perform multiple tasks, reducing readability.
3. Large Class: A class with too many responsibilities, violating the Single Responsibility Principle.
4. Feature Envy: A method that relies excessively on data from another class.
5. Primitive Obsession: Overuse of primitive data types instead of creating proper abstractions.
6. Switch Statements: Excessive use of conditional statements that could be replaced with polymorphism.

How to Address Code Smells:
1. Refactoring: The primary approach to dealing with code smells is refactoring—improving the structure of existing code without changing its external behavior.
2. Adopting Design Patterns: Using appropriate design patterns can help resolve many common smells, such as replacing switch statements with the Strategy pattern.
3. Code Reviews: Regular peer reviews help identify smells early in the development cycle.
4. Automated Tools: Tools like SonarQube and PMD can automatically detect code smells and suggest improvements.

Benefits of Fixing Code Smells:
1. Improved Readability: Clean code is easier for developers to understand and work with.
2. Reduced Bug Risk: Well-structured code reduces the likelihood of introducing bugs during modifications.
3. Enhanced Scalability: Clean code is easier to extend and adapt to changing requirements.

Example:
If a function named calculateAndPrintInvoice() handles both the calculation and the printing of an invoice, it violates the Single Responsibility Principle. Refactoring it into separate methods for calculation and printing would eliminate the code smell.

By proactively addressing code smells, developers ensure that their applications remain robust, maintainable, and adaptable to future changes.