Microsoft Groups are core to many Office 365 services. When you create a Microsoft Team it creates a Group. When you instantiate and instance of Planner you guessed it, you get a group. Groups provide core services and access for services such as Planner and Teams. In instances where organizations have enabled employee self service for the creation of Teams, Planner, etc. (and I highly recommend they do!) IT administration can sometimes become concerned around the management and policy settings that need to be put in to place to avoid potential sprawl. Thankfully though Microsoft has put in to place all the tools needed to deal with groups from creation to management to expiration.
If you and your organization are looking to get a handle creation, management, and expiration of Groups the following resources will not only explain how to do so but will also provide the actual scripts and more.