BranchCache is a WAN bandwidth optimization technology included in certain versions of Windows Server 2016, Windows 10, and earlier Windows operating systems. It is designed to reduce bandwidth usage on networks by caching frequently accessed information and files locally on servers and clients. To configure BranchCache, administrators must determine settings like the amount of cached copies, maximum cache size, and whether to apply caching to specific folders. BranchCache works by leveraging local storage to cache content from remote locations, decreasing the amount of data that needs to be transmitted across the network.