AWS Lambda Aliases enable you to route traffic to different versions of a Lambda function. Aliases are like pointers and can be changed to point to different function versions as needed. This is useful for integration testing as you can maintain separate testing environments without changing the function's ARN, thus ensuring the stability and consistency of your application during the testing phase. Using different function versions or Stage variables are incorrect choices because while they can point to different configuration settings or Lambda versions, they do not offer the same aliasing capability for routing across different environments without altering the ARN.