WIM, short for Windows Imaging Format, is a file-based disk image format similar to VHD, VDI, and TIB.
The format was developed by Microsoft and works with Windows 7, Vista, and Server 2008.
Making it different than ISO or BIN/CUE, a WIM file is file based and not sector-based, meaning that smallest unit of info is a file. The competitive advantages of this are hardware independence and unique storage.
WIM files can also, uniquely, contain multiple disk images in one, referenced by a manually written unique name or numerically indexed.
Multiple disk image files have SWM extensions.
WIM images can be mounted as new drive letters in supported OSs, making addition to the files much easier.