Answer is pretty simple, if you own a company XYZ which provides AdWords campaigns services whatever but related to AdWords advertisements. In the same time your company or you have no knowledge how to do that task or how to deliver that AdWords campaigns services to their clients. Then your company find someone outside the company it can be any freelancer or any other person who has brilliant expertise in that domain that strategy would be known has white Label AdWords Management.
Because you are outsourcing for that domain experts but in the same time you are getting clients with this AdWords campaign services so that strategy is really good and effective, if your second Arms (Outsource freelancers) are good enough to deliver their services in right manner.
Hope that will help you!